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Hello,

I am looking for some assistance with determining whether the ignition switch on a Murray Lawn tractor (model # 40508x92G) is good or bad.

What I need to know specifically is what positions should give continuity and which ones shouldn't.

I have included the factory electrical diagram for my mower, and AFAIK ( I won't assume anything) it is correct for my mower. I double checked the wire colors on the harness and they do match what is shown on the attached diagram 100%

If someone sees that a simple continuity check for this particular switch/circuit would be inconclusive in knowing 100% whether the switch is ok or not, please point that out to me.

In case anyone is wondering, what happens is turning the key to start does absolutely nothing, just a small click - no engine turn over, nothing. Fuse is GOOD, The battery tests strong (12.75V), and, I think I have ruled out the solenoid. There is full voltage coming into the solenoid (RED lead), but I get no voltage on the ORG lead (when disconnected and measured as I turn key to START). Maybe the PTO safety switch but I want to rule out the ignition switch first.

Thanks,

Alan

I think you can rule out ignition switch because you are getting a click...!
You can check this by taking off the small lead on solenoid and seeing if you have battery volts on the lead when key is in start.
Give the ground lead a good clean and take off the solenoid and where it bolts to ground give that also a good clean and the big leads, and if that does'nt do the tick replace solenoid.
I don't think its a safety switch because you are getting a click, if one of the safety switch(s) was open you wouldn't get a click at solenoid.

Have a look at this post and you will see.......

http://www.lawnmowerforum.com/small...have-12-volts-but-still-starting-problem.html

I think you can rule out ignition switch because you are getting a click...!
You can check this by taking off the small lead on solenoid and seeing if you have battery volts on the lead when key is in start.
Give the ground lead a good clean and take off the solenoid and where it bolts to ground give that also a good clean and the big leads, and if that does'nt do the tick replace solenoid.
I don't think its a safety switch because you are getting a click, if one of the safety switch(s) was open you wouldn't get a click at solenoid.

Click to expand...

I would have thought so too, but as I had said, when I did the voltage check on the small solenoid lead as you described I got 0 volts when the key was turned to START which would seem to point elsewhere since the voltage is not getting there.

I checked ground continuity from solenoid mounting bolts to several points of bare metal on the chassis and they all checked good. I will go now and check the ground lead on the switch wiring harness and see if tests good to the solenoid frame bolts.

Also wanted to add that when doing a continuity check with the switch in the OFF position I'm getting a very dodgy reading from Ground (pin 6) to Stator (Pin 4), which I think should be a clean low ohm reading for OFF? I'm getting anything from 24ohms to 3K to 5.6M (essentially open). Moving the key causes it to jump around indicating a poor contact. Perhaps the internal Ground connection in the switch is bad. Any thoughts?

Ground (pin 6) to Stator (Pin 4), is just for you're light's, have you got 12v at pin 2, if so check the safety switch(s)

Ok. I'm getting no continuity from the switch harness ground wire to the solenoid frame or to other bare metal chassis points. Unless I'm misreading the schematic it would appear to be a bad ground connection.

Would that be the Black wire...?

Find some wire, about 12in long, bear off both ends and fold back, take off small lead on solenoid hold one end on the small connecter that you took of the wire off from, now with ignition switch off, touch with other end the big lead that come's from the battery to the soleniod, engine should turn over.

The single black wire with O ring connector shown in the pic is the other end of the switch harness ground wire. It had apparently come loose - but from where is a bit of mystery at the moment. There is no clear obvious place of connection. Both of the solenoid frame bolts are tightly secured and there are no other loose bolts or bolt holes that I can see in the proper locale. There are only two frame screws (conical ended sheet metal type with no bolt) that are within reach of the ground wire. I suppose it does not matter where I reattach the ground provided it is well secured and stable. Any thoughts on where it likely was originally?

The single black wire go's to ground, if it fit's one of the bolt's that hold the solenoid on put it there.
Going by the wiring diagram it go's on solenoid ground as above....!

I secured the loose ground wire to the solenoid frame. Still will not start.

Also still No Voltage on small solenoid hot lead when measured while turning key to START.

Ground (pin 6) to Stator (Pin 4), is just for you're light's, have you got 12v at pin 2, if so check the safety switch(s)

Click to expand...

I do have 12V at pin to, so on to safety switches. I wonder if the ground coming loose caused failure of one of the safety switches. Seems unlikely to have them both go out at same time.

Any suggestions on how to test the switches, assuming I can reasonably access them?

Set you're meter to Ohm's 1 connect one end to Orange lead that you have taken off solenoid, and the other to Pin 5 on the ignition switch, which is also Orange, you should have continuity, if you don't you have a bad wire between there going to all safety switch(s) or a safety switch that is open. so work you're way back from Orange lead at solenoid to Pin 5 ignition switch. checking each safety switch in turn.

Did you do what I said to do in post #6 if you do that, we can come away from it knowing it works.....with me...?

MTD said:

I secured the loose ground wire to the solenoid frame. Still will not start.

Also still No Voltage on small solenoid hot lead when measured while turning key to START.







I do have 12V at pin to, so on to safety switches. I wonder if the ground coming loose caused failure of one of the safety switches. Seems unlikely to have them both go out at same time.

Any suggestions on how to test the switches, assuming I can reasonably access them?

Click to expand...

I think at some point someone had renewed the sloenoid and forgot to refit the ground lead.
the way to test safety switch, there will be a Orange wire going in, and a Orange wire coming out, set meter to Ohm's and connect leads to both wire's you should have continuity when you push or release the switch.

Do you have power coming from Pin 5 ignition switch when you turn the key to start..? very important. Man am working hard here...!
And where is Rivets when I need him...!:wink:

EngineMan said:

Did you do what I said to do in post #6 if you do that, we can come away from it knowing it works.....with me...?

Click to expand...

Ok. Did as advised and it turns over.

I think at some point someone had renewed the sloenoid and forgot to refit the ground lead.
the way to test safety switch, there will be a Orange wire going in, and a Orange wire coming out, set meter to Ohm's and connect leads to both wire's you should have continuity when you push or release the switch.

Click to expand...

I can access ORG wire on switch harness but other ends will be tricky. So far I can only find the blade/deck switch, which I think is marked PTO on schematic.

Ok so we know now that the solenoid will work when it gets power, so now take you're time and check wire and safety switch(s) do a continuity test at Orange wire on safety switch one of them will have continuity back to the end of the orange wire that fits on solenoid, and keep checking on each switch, make sure you have power from Pin 5 when you turn the key to start, if you don't have power there its the switch you need to renew.
Not sure how long you are going to work on this today, but let me know, so I can come away from the post.

EngineMan said:

Ok so we know now that the solenoid will work when it gets power, so now take you're time and check wire and safety switch(s) do a continuity test at Orange wire on safety switch one of them will have continuity back to the end of the orange wire that fits on solenoid, and keep checking on each switch, make sure you have power from Pin 5 when you turn the key to start, if you don't have power there its the switch you need to renew.
Not sure how long you are going to work on this today, but let me know, so I can come away from the post.

Click to expand...

I located safety switches and will try a continuity check. I'm not sure there is a way to verify power on pin 5 when key is turned to start. The harness must be plugged in to back of switch so there's no access to that wire. I still suspect the possibility of a faulty ignition switch. I'm going to have to call it a day for today but should return tomorrow first thing. Thanks again EngineMan for your help so far.

Should'nt need to have harness plugged in you can do a continuity test just with the key switch across 2 and 5. with switch in start.
Its always best to go over things slowly so take you're time, I'll be around tomorrow.

make sure you have power from Pin 5 when you turn the key to start, if you don't have power there its the switch you need to renew.

Click to expand...

If I am following you, there is not. I'm basing this on the fact that I removed the small orange wire from the solenoid and measured voltage there while turning the key to START and got no voltage.

I have removed the old switch and strangely enough I get good continuity from pin 2 (hot from battery) and pin 5 (solenoid) when key is turned to START. However, the connection between pin 4 (M) and pin 6 (Ground) in the OFF position is very dodgy - sometimes it will read a few ohms, then jump to MegaOhm readings and is sensitive to key jostling. I know this is for STOP but could this prevent start as well?

Pin 4 is the kill wire, I think you may need a new ignition switch. to start of with.

I just picked up a new switch and will say more about that in a moment.

I just completed a check of the safety switch ORG path.

Brake Switch: checks GOOD

Path from Solenoid wire (org) on switch harness to Brake Sw: GOOD

Path from small org solenoid wire to brake sw (via the PTO/blade sw): GOOD. I did this by simply lowering the deck so switch and connection look ok.

Yellow Wire Path:

From Magneto wire (two Yel) on back of key switch harness to Ground shows continuity in BOTH seat positions. I may not be understanding the schematic but shouldn't the ground connection on this leg open when the seat switch is pressed ( sitting on the seat) ?

I still need to pull the switch out and test the positions which I will now do.

When you sit on the seat switch there is no path to kill engine (yellow wire), the switch is open

Well it appears that there is an internal short inside the brake safety switch harness connector . . .

The switch itself functions properly. Testing the harness gives continuity between the incoming and ground leads and it shouldn't be there.

As far as a fix for this, it should be quite easy to attach some spade connectors to the ends of the incoming leads for attachment to the switch. Access to the wires is difficult without removal of frame and tires.

Could you suggest a safe temporary fix for this?

If you say its in the wiring and not the switch, try taking a wire from Pin 5 (orange) (in) on clutch brake switch, to (orange) (out) on pto switch, that should cut out the main orange feed wire from pto-clutch/brake but would still leave you with safety switch pto and seat. I think I have that right...!
But remember you will have to take out the bad wire if you say its going to ground.
Have you got now, with new ignition switch full battery power out of Pin 5 when you turn to start..?

After poking around some more I have found an easy way to properly repair the internal short in the switch harness, so rigging up a temp shouldn't be necessary.

I would just like to confirm once more that:

Sitting on the seat should OPEN the ground connection of the yellow wires. Is this correct?

I will repair the bad wires and try and start her up later this evening. I have to be away for a bit shortly but will post back later.

MTD said:

After poking around some more I have found an easy way to properly repair the internal short in the switch harness, so rigging up a temp shouldn't be necessary.

I would just like to confirm once more that:

Sitting on the seat should OPEN the ground connection of the yellow wires. Is this correct?

I will repair the bad wires and try and start her up later this evening. I have to be away for a bit shortly but will post back later.

Click to expand...

By seating on the seat you don't kill the engine....if that is what you are asking then yes.
You can always put two new wire's in from the switch(s) if you feel they are bad.
But if you have power now at Pin 5 when you turn the key to start, there is a way short cut but only if the bad wiring doesn't kill the coil...!

I see you already have a lot of advice on this but if you are testing the ignition switch you have to remember you have three different types of voltage going to it. DC positive Voltage, AC positive voltage, and negative voltage. each has its own test and does its own thing. #1 Black is negative feed wire, #2 Red DC positive voltage feed wire, #3 white AC positive voltage feed wire, #4 yellow negative turns off mower engine, #5 orange DC positive activates starter solenoid after it go through safety switches, #6 violet DC positive voltage goes to lamps. Its not hard but you just have to think what type of voltage are you looking for and what does it do. A lot of people don't think as the negative as a voyage but it is and it is just as important as the positive side.

If he has full battery volt's in at Pin 4, but very little out of Pin 5, he got a bad switch.....yes..?

THE ABOVE IS WRONG, IT SHOULD BE PIN 2 AND NOT PIN 4......!

EngineMan said:

If he has full battery volt's in at Pin 4, but very little out of Pin 5, he got a bad switch.....yes..?

Click to expand...

Ether its the wrong wiring diagram, somethings not wired right or you have the wrong switch. Pin 4 should be negative power when switch is in off position and pin 5 should have full DC voltage when in the starter position. With positive power to the coil module on pin 4 you will destroy the module. After voltage goes through pin five it looks like it through two safety switches before it goes to the starter solenoid. These test should be done with a multi-volt meter so you know what type of voltages you are working with.

I put the new connectors on the seat safety switch wires and still, I'm shorting to ground in both positions.

So I pulled the the two yellow leads loose and checked the one coming from the Magneto (pin 4_ and there is a path to ground somewhere else in the line . . . From the schematic I cannot see any other path to ground so I am at a dead end for the moment.

Unless I'm misreading the schematic, what I see for the yellow wire path starting at pin 4 (magneto) is a NC circuit through all 3 of the safety switches with a SINGLE ground point coming out of the seat switch. Yet, I am reading TWO. NOTE: the ignition switch was NOT connected to the harness for these measurements. If it were, then Pin 4 would normally be shorted to ground.

The switch connector I pulled loose does actually show an internal short. This suggests the possibility that too much current was pulled (but not enough to open the fuse) and caused an internal short. Or, that it was supposed to be that, though that would seem to make no sense- the switch would be useless.

One would also think the fuse rating matched the breakdown current rating for the switches to prevent internal shorting.

reynoldston said:

Ether its the wrong wiring diagram, somethings not wired right or you have the wrong switch. Pin 4 should be negative power when switch is in off position and pin 5 should have full DC voltage when in the starter position. With positive power to the coil module on pin 4 you will destroy the module. After voltage goes through pin five it looks like it through two safety switches before it goes to the starter solenoid. These test should be done with a multi-volt meter so you know what type of voltages you are working with.

Click to expand...

The only voltages I have confirmed on the switch are that there is +12.75 on pin 2, and that there is 0 volts reaching the small org solenoid wire. I still need to check whether there is voltage coming out of the switch at pin 5 ( to differentiate bad switch from bad path to solenoid switch. Up until now I did not have the harness in an accessible place to safely test this. I would like to get the seat safety switch ground issue solved before trying in case there is something (short) that needs to be repaired.

You got so many things going here that its hard to keep up. OK now lets start with the yellow wire. The yellow wire is negative power, no 12volt positive power to the yellow wire at all. Places it picks this negative power from is from the #4 pin through the ignition switch from the black wire #1 and also through the seat switch through the switch from the mower chassis. The mower chassis is negative power from the battery. Also this wire gos through the PTO and clutch safety switch. Now also you have a orange wire going through the PTO and clutch safety switches which is 12 volt positive which starts from pin #5 and goes to the starter solenoid. Now for the confusing part. The PTO and clutch have two positions on them that are on and off with 4 poles which work just the opposite from each other.

What I missed was that the magneto pin 4 is grounded via the armature. I missed that path on the schematic. Too much time on the heat today. :confused2:

Sorry for the confusion.

MTD said:

What I missed was that the magneto pin 4 is grounded via the armature. I missed that path on the schematic. Too much time on the heat today. :confused2:

Sorry for the confusion.

Click to expand...

I know the wire schematics is very confusing but the coil and armature are two different parts and yes the Armature is grounded to the engine. The coil itself is not grounded and if it is the mower wouldn't run. That is what turns off the engine is when the coil is grounded through pin #4 the yellow wire. What I am trying tell you is the yellow wire picks up the ground when you turn the switch to off throught the igntion switch from the black wire #1.

OK it seems we are getting nowhere with this because it seems to me you are not that familiar working with electric. Lets start from the beginning and just what is your problem?? Is the battery good, battery cables and connections, starter solenoid, all wire connections, any broken wires or loose plugs??? Start small As I recall you wanted to know how to check your ignition switch to see if it was bad and now you are getting into the coil wiring which would have nothing to do with if the starter turns the engine over or not. Lets keep it to one thing at a time and you will have better luck with this and not jump all over the place.

You got so many things going here that its hard to keep up

Click to expand...

Yes, this thread has gotten confusing because of so many questions and side tracking in different directions. Maybe best if we start afresh by keeping the basic information straight.

Lets start from the beginning and just what is your problem??

Click to expand...

It's right there in post #1

1st question: not answered.

What I need to know specifically is what positions should give continuity and which ones shouldn't.

Click to expand...

clear explanation of what I had done before asking if someone could decipher what readings I should get on the ignition switch >>out of circuit<< to tell whether I had a bad switch or not.

In case anyone is wondering, what happens is turning the key to start does absolutely nothing, just a small click - no engine turn over, nothing. Fuse is GOOD, The battery tests strong (12.75V), and, I think I have ruled out the solenoid. There is full voltage coming into the solenoid (RED lead), but I get no voltage on the ORG lead (when disconnected and measured as I turn key to START). Maybe the PTO safety switch but I want to rule out the ignition switch first.

Click to expand...

Post #3 - where I repeated the information I had just given . . .

I would have thought so too, but as I had said, when I did the voltage check on the small solenoid lead as you described I got 0 volts when the key was turned to START which would seem to point elsewhere since the voltage is not getting there.

Click to expand...

Post #14 - Now we know the solenoid is ok

Find some wire, about 12in long, bear off both ends and fold back, take off small lead on solenoid hold one end on the small connecter that you took of the wire off from, now with ignition switch off, touch with other end the big lead that come's from the battery to the soleniod, engine should turn over.

Click to expand...

Ok. Did as advised and it turns over.

Click to expand...

Post # 20 - Now we know the NC and NO safety switch paths are good

I just completed a check of the safety switch ORG path.

Brake Switch: checks GOOD

Path from Solenoid wire (org) on switch harness to Brake Sw: GOOD

Path from small org solenoid wire to brake sw (via the PTO/blade sw): GOOD. I did this by simply lowering the deck so switch and connection look ok.

Yellow Wire Path:

From Magneto wire (two Yel) on back of key switch harness to Ground shows continuity in BOTH seat positions. I may not be understanding the schematic but shouldn't the ground connection on this leg open when the seat switch is pressed ( sitting on the seat) ?

Click to expand...

And for the current post, in answer to questions:

From post #28

pin 5 should have full DC voltage when in the starter position.

Click to expand...

From post #23

Have you got now, with new ignition switch full battery power out of Pin 5 when you turn to start..?

Click to expand...

Yes, I have full battery power coming OUT of the ignition switch when the key is turned to START

OK it seems we are getting nowhere with this because it seems to me you are not that familiar working with electric.

Click to expand...

You sure about that?


I will start again tomorrow. It's very easy to miss things when working inside a storage building when its 95 deg outside. Hopefully it will be something simple. Has to be.

Thanks again to everyone for their patience and help!

reynoldston said:

Ether its the wrong wiring diagram, somethings not wired right or you have the wrong switch. Pin 4 should be negative power when switch is in off position and pin 5 should have full DC voltage when in the starter position. With positive power to the coil module on pin 4 you will destroy the module. After voltage goes through pin five it looks like it through two safety switches before it goes to the starter solenoid. These test should be done with a multi-volt meter so you know what type of voltages you are working with.

Click to expand...

Sorry it should have been Pin 2 and not Pin 4, my mistake...! The key's on the keyboard keep moving

In post 1 "What I need to know specifically is what positions should give continuity and which ones shouldn't."

Key off......Pin 4 continuity to ground (pin 6)
Key on..... no continuity to ground and no continuity between pin 2 & pin 5
Light's off...no continuity from pin 3 to pin 1
Light's on...continuity at pin 3 to pin 1
Key to start continuity from pin 2 to pin 5

Just stay cool, am sure you know how to use a meter, and you will get there...!

I will start again tomorrow. It's very easy to miss things when working inside a storage building when its 95 deg outside. Hopefully it will be something simple. Has to be.


As I see it you have the hard part taken care of, you have a wiring diagram. If you can follow a wiring schematics just follow the wire colors. I find elrctric is very easy to work with if you have something to follow and under stand it. Of course I repaired electric fork trucks for over ten years. I keep trying to tell you you have to konw what type of electric you are working with and you keep going about continity.

As I see it you have the hard part taken care of, you have a wiring diagram. If you can follow a wiring schematics just follow the wire colors. I find elrctric is very easy to work with if you have something to follow and under stand it. Of course I repaired electric fork trucks for over ten years. I keep trying to tell you you have to konw what type of electric you are working with and you keep going about continity.

Click to expand...

I am getting 12V out of the switch on the org wire when turned to START

I get 0 volts at the solenoid small org wire when turned to START.

It was my understanding that I should get 12V at the small org solenoid wire when turned to START.

What's confusing me is that, if you look at the schematic and follow the org wire from the ignition switch all the way around to the small solenoid wire you can clearly see that the PTO is Normally OPEN when disengaged. So i see no way you can have 12V here unless you engage the blade because it's an OPEN circuit. I'm not trying to be confusing, I'm just following the advice given by EngineMan in post # 2

You can check this by taking off the small lead on solenoid and seeing if you have battery volts on the lead when key is in start.

Click to expand...

And given here in this you tube video:

How to test a lawn mower solenoid - YouTube



Whatever the case may be, I get 0 voltage on the small solenoid lead when the key is in START. I checked the entire org wire path for continuity and it checks GOOD, and so do the switches.

Maybe you can explain what is supposed to happen electrically when I turn the key to START, because I don't understand how you can get 12V to the small solenoid lead through an OPEN circuit. What do I need to look for next?

reynoldston said:

I will start again tomorrow. It's very easy to miss things when working inside a storage building when its 95 deg outside. Hopefully it will be something simple. Has to be.


As I see it you have the hard part taken care of, you have a wiring diagram. If you can follow a wiring schematics just follow the wire colors. I find elrctric is very easy to work with if you have something to follow and under stand it. Of course I repaired electric fork trucks for over ten years. I keep trying to tell you you have to konw what type of electric you are working with and you keep going about continity.

Click to expand...

I would have to disagree with you, knowing if you are working with AC or DC will not tell you if a switch is working or not.
A meter set to Ohm's is the best and safer way to test. if you know how to use them.
The only problem that I see is that he has to decide if he is going to use Volts (power) to test or a meter set to Ohm's. (resistance). and not have too many cook's coming into the kitchen.

A simple DMM for volts and ohms has served just fine.

12V at the small org solenoid wire when key is turned to START, I still don't see it happening with the PTO being NO when disengaged. What am I missing? Also, though it is often assumed, clutch pedal should be pressed when performing this test. The youtube video doesn't even mention this.

As you say and you are right, if any of the safety switch(s) are open, there will be no path for power(12v+) to go to solenoid. that is why you need to check all safety switch(s) one by one until you find the one (maybe two) that are open.
I have no plans in leaving you until you have fix it, or you have given up on it. so keep working at it:thumbsup:

This may also help you, work out by two good member's on this site.

Electrical* problems can be very easy or very difficult, depending on four things.
1. * How well you understand basic electricity.
2. *What tools you have and know how to use.
3. *How well you follow directions.
4. *You don't overlook or assume anything and verify everything.

Remember we cannot see what you are doing. *You are our eyes, ears and fingers in solving this problem. *You must be as accurate as you can when you report back. *The two basic tools we will ask you to use are a test light and a multi-meter. *If you have an assistant when going through these tests it would be very helpful. *These steps work the best when done in order, so please don't jump around. *Now let's solve this problem.

First, check the fuse(s), check battery connections for corrosion (clean if necessary) and *voltage - above 12.5 volts should be good.*

Second, check for power from the battery to one of the large terminals on the solenoid. *One of the wires is connected directly to the battery and has power all the time so one of the large terminals should light a test light or show 12 volts on a meter at all times.*

Third, *check for power at the small terminal of the solenoid while depressing the clutch/brake pedal and holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch). If your solenoid is a four wire solenoid, check both small wire terminals as one is ground and the other is power from the ignition switch. *If your solenoid is a three wire solenoid, make sure the solenoid body is not corroded where it bolts to the chassis of the mower as this is your ground path back to the battery. *If in doubt, remove the solenoid and clean the mounting area down to bare metal. *If there is no power to the small terminal then your problem is most likely a safety switch, ignition switch or in the wiring.*

Fourth, check for power on the other large terminal of the solenoid while holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch).*

Fifth, check for power at the starter while holding the key in the start position (assistant again).*

Sixth, check your ground circuit back to the battery.

After you have gone through each of the above steps, let us know what happened when you did each step. *At that point we will have great info to tell you how to proceed. *Remember you are our eyes, ears, and fingers, so please be as accurate as possible.

Be as specific as possible with voltage readings as this will help diagnose your problem quicker. *If you do not know how to perform the above checks, just ask and I will try to guide you through it. *Youtube also has some videos and as you know a picture is worth a thousand words.

EngineMan said:

As you say and you are right, if any of the safety switch(s) are open, there will be no path for power(12v+) to go to solenoid. that is why you need to check all safety switch(s) one by one until you find the one (maybe two) that are open.
I have no plans in leaving you until you have fix it, or you have given up on it. so keep working at it:thumbsup:

Click to expand...

EngineMan, you asked me specifically earlier in the thread:

You can check this by taking off the small lead on solenoid and seeing if you have battery volts on the lead when key is in start.

Click to expand...

Please try and understand what I am asking:

Look at the diagram:

You will see that the PTO is NORMALLY OPEN in the starting position. Normally opens means there will be NO VOLTAGE passing through the circuit. so,

WHY SHOULD I EXPECT TO READ FULL BATTERY VOLTAGE ON THE SMALL SOLENOID WIRE WHEN TURNING THE KEY TO START WHEN THE PTO IS AN OPEN CIRCUIT IN ITS STARTING POSITION?

I am with you and do understand what you are saying, that switch (circuit) need's to be closed.

EngineMan said:

This may also help you, work out by two good member's on this site.

Electrical* problems can be very easy or very difficult, depending on four things.
1. * How well you understand basic electricity.
2. *What tools you have and know how to use.
3. *How well you follow directions.
4. *You don't overlook or assume anything and verify everything.

Remember we cannot see what you are doing. *You are our eyes, ears and fingers in solving this problem. *You must be as accurate as you can when you report back. *The two basic tools we will ask you to use are a test light and a multi-meter. *If you have an assistant when going through these tests it would be very helpful. *These steps work the best when done in order, so please don't jump around. *Now let's solve this problem.

First, check the fuse(s), check battery connections for corrosion (clean if necessary) and *voltage - above 12.5 volts should be good.*

Second, check for power from the battery to one of the large terminals on the solenoid. *One of the wires is connected directly to the battery and has power all the time so one of the large terminals should light a test light or show 12 volts on a meter at all times.*

Third, *check for power at the small terminal of the solenoid while depressing the clutch/brake pedal and holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch). If your solenoid is a four wire solenoid, check both small wire terminals as one is ground and the other is power from the ignition switch. *If your solenoid is a three wire solenoid, make sure the solenoid body is not corroded where it bolts to the chassis of the mower as this is your ground path back to the battery. *If in doubt, remove the solenoid and clean the mounting area down to bare metal. *If there is no power to the small terminal then your problem is most likely a safety switch, ignition switch or in the wiring.*

Fourth, check for power on the other large terminal of the solenoid while holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch).*

Fifth, check for power at the starter while holding the key in the start position (assistant again).*

Sixth, check your ground circuit back to the battery.

After you have gone through each of the above steps, let us know what happened when you did each step. *At that point we will have great info to tell you how to proceed. *Remember you are our eyes, ears, and fingers, so please be as accurate as possible.

Be as specific as possible with voltage readings as this will help diagnose your problem quicker. *If you do not know how to perform the above checks, just ask and I will try to guide you through it. *Youtube also has some videos and as you know a picture is worth a thousand words.

Click to expand...

. . . same thing

All you need to do is to check to see if you have power on both side's of the switch(s) on orange wire's, if you do not switch maybe bad or not set for start.(open circuit)
I know that they are sometimes difficult to get at, but it's the only way...!

EngineMan said:

All you need to do is to check to see if you have power on both side's of the switch(s) on orange wire's, if you do not switch maybe bad or not set for start.(open circuit)
I know that they are sometimes difficult to get at, but it's the only way...!

Click to expand...

I have full voltage coming in to the switch at pin 2 (red), and I get full voltage coming out of the switch at pin 5 (org) when the key is turned to START.

That's good, now all you need to do now is to make sure that the contacts of switch(s) clutch/brake and pto are closed so that there is a path for power to go to orange wire on solenoid.

EngineMan said:

That's good, now all you need to do now is to make sure that the contacts of switch(s) clutch/brake and pto are closed so that there is a path for power to go to orange wire on solenoid.

Click to expand...

This is what I have been trying to point out - the PTO is OPEN when the blade deck is raised (START position). In order to close the PTO I have to lower the deck and engage the blade. This is what makes no sense to me and I must be missing something. The schematic is correct. I verified this by checked the PTO switch with an ohmmeter - the PTO is open circuit when the deck is raised.

This is purely for my interest, will it turn over if you lower the deck...?

EngineMan said:

This is purely for my interest, will it turn over if you lower the deck...?

Click to expand...

I had the very same curiosity and checked this - but only with the solenoid small wire disconnected. I just wanted to see if this allowed voltage to the solenoid. It did not.

Would it make a difference checking with the solenoid wire attached to the solenoid?

Do you have power at small lead (orange lead) at solenoid when you have the deck down and try the key in start. You should have battery volts.
If not there is no need to try what you are thinking of doing.

EngineMan said:

Do you have power at small lead (orange lead) at solenoid when you have the deck down and try the key in start. You should have battery volts.
If not there is no need to try what you are thinking of doing.

Click to expand...

Well, I had checked this before and did not, but I just checked again and, Yes - I get full voltage at the solenoid small wire when cranking with the deck DOWN.

I'm not too keen on attempting to start the mower with the deck down.

How in the world did it start before with the switches wired the way they are is what I'm trying to figure out.

MTD. I have been following this thread for some time and have stayed out because I didn't want to confuse things, but thought I might be able to help if you want it. I am one of the people on this forum who worked on the steps to solve electrical problems posted earlier. It you don't want me around and feel that I am butting in, let me know and I will be gone. Just to let you know that I wil be asking you to do things that have been done before. If you would like my help, please do the following two things and post back yes I want you here. If you want me to stay out of it please say so and I am gone, because I know that it can get very confusing. Rivets

Two things I would like you to do.

1. Reread the post #42 and tell me it you understand want each step is telling you. DO NOT DO EACH STEP.

2. Read the following and look at the schematic. Do you follow what I am saying.


Here is my answer to start this engine.
1. Body on the seat, safety switch open, so current cannot go to ground.
2. Brake pedal is down to close the NO side of the Clutch Brake Switch.
3. Mower deck is in the up position to close the NO side of the PTO Switch.
4. With this all in place current will come into the Key Switch at Terminal #2
5. With the Key in the Start Position the current will go through the Key Switch out Terminal #5.
6. It will travel through the orange wire through the closed Brake Switch, through the orange wire to the closed PTO Switch, through the orange wire to the small terminal of the solenoid.
7. This will energize the coil in the solenoid and the starter should turn.

Let me know if you want me in or out.

Rivets, am sure you are not "butting in" I for one welcome you......so please do help.:thumbsup:

It seem's that the engine will turn over, but only when the deck down, and as you say Rivets in the above.....3. Mower deck is in the up position to close the NO side of the PTO Switch.

It seems as MTD is finding out..........very odd....!

Hi Rivets, glad to have you join in!

First, I want to point out something critical in your directions:

3. Mower deck is in the up position to close the NO side of the PTO Switch.

Click to expand...

This is where we seem to be stuck because if you look at the schematic it seems to be showing opposite of what you said. The PTO is shown as NO when the deck is raised and in the SAFE/START disengaged position.

I confirmed what the schematic is showing by doing both a continuity check and and voltage check and it is apparently correct - the PTO is OPEN when the deck is disengaged which gives an OPEN circuit in the cranking path to the solenoid.

Where should I proceed from here?

Ok, I'm in. First, you must remember not to assume anything. The schematic shows the PTO switch in the disengaged position. When you raise the deck to the up position you engage this switch, where it needs to be to start the engine. By disengaged they mean in the normal operating position, NOT for starting. That said, here goes.

As I read your posts my first question is, is the key switch the correct one. The first thing I would like you to do is take the key switch and verify each terminal is in the correct position as the schematic. If you look at the switch you have out of the engine, this is what you should see on either the terminals or on the back of the switch.
Terminal #1 should be labeled L or A for lights or accessories
Terminal #2 should be labeled B for battery
Terminal #3 should be labeled L or A for lights or accessories
Terminal #4 should be labeled M for magneto
Terminal #5 should be labeled S for starter
Terminal #6 should be labeled G for ground

Please check each of these carefully, as this will tell us our next step. I spent 34 years teaching this stuff to people ranging from 11 - 60 years old. My methods are crazy and at times people didn't like to do it my way, but when I'm done it will be running. Remember slow and patience. Post back what you find and we will go to the next step.

When the engagement lever is pulled up to raise the deck, it will contact the safety switch to put it in the engaged position. Let's stay away from the switches at this point and work our way down the list first. If we jump around we will miss something, happens every time, sorry but that's why they call me crazy.

The one on the right is the original switch. The new one on the left is a current replacement for comparison.

The original does not have any visible numbering or lettering. The lettering may have gotten worn off.

The wiring to the switch matches exactly what is shown on the schematic I posted:

top center: Magneto (two yellow wires)

top left: Aux (white wire)

top right Solenoid (orange wire)

bottom left: Hot lead B to battery (two red wires)

bottom right: Lights (violet wire)

bottom center: ground (two black wires)


I have got the PTO switch out now to clean, and need to clean and blow out the inside of the harness. There seem to have been some extra wires taped and tucked against the bottom side of the switch and coming out of the harness . . . . I wonder if they have been added by previous owner. I've only had this mower a month or two. I'll report back in a bit after I figure out what's going on.

For some reason one one understands you have two different types of voltage going through the PTO and Clutch switches. not AC and DC but positive and negative. It is very easy to follow the wiring diagram and very clear how this all works. This is all basic simple switches and no computers. A switch is on or off a very simple device maybe the best way I can explain this is like a water valve in a pipe. I would guess just run a jumper wire from #5 to the starter solenoid and see what you get. Nothing to burn out unless you put positive voltage to the coil #4 yellow wire which as I recall runs through these same two switches plus the seat switch. Also you must understand you need more then voltage through any wire or switch you also need enough amps to operate the device you are operating. Amps is the amount of flow.

Ok, we know that the switch is the correct one. Let's go to the first test. Make sure that the fuse is good. You will need to put some weight on the seat to close the seat safety switch. Put the brake/clutch pedal in the down position and apply the parking brake. Raise the deck to the highest positions. If I remember this unit correctly, raising the deck also sets the parking brake. Hope I am right, but is does not matter. Use a test light if you have one for this test. If you don't have one, you can use the multi-meter as a test light by setting it to 20V DC and connecting the ground lead to the negative terminal of the battery. With the key in the start position check for 12+V at the small terminal of the solenoid. If you have 12V your starter should kick in. If not we start back tracking to the key switch. How??? In this order, follow the orange wire back to the PTO switch and test both orange terminals for 12V. Follow the orange wire back to the brake switch and again check for 12V. Follow the orange wire back to terminal #5 (S) of the key switch and check for 12V. Post results and we will continue.

Reynoldston, if you look carefully at the schematic you will see that there is AC current coming from the stator to terminal #3 and leaving terminal #1 going to the lights. This switch has a turnback position to turn on the lights using AC current. This part of the switch has nothing to do with the starting or running of the engine. I think MTD may be getting confused because of this set-up and that is why I am just taking him through the DC systems and forgetting about the AC side at this time.

Reynoldston, if you look carefully at the schematic you will see that there is AC current coming from the stator to terminal #3 and leaving terminal #1 going to the lights. This switch has a turnback position to turn on the lights using AC current. This part of the switch has nothing to do with the starting or running of the engine. I think MTD may be getting confused because of this set-up and that is why I am just taking him through the DC systems and forgetting about the AC side at this time.



I don't know what in the world AC and DC has to do anything. The alternator or stator puts out the AC. This is what I am saying 12 volt POSTIVE and 12 volt NEGATIVE. NOT AC AND DC. With out the NEGATIVE side you just don't have anything. Not only does the chassis carry NEGATIVE voltage but wires do also. Now if you are working with computer operated systems like on newer motorcycles without a proper ground or NEGATIVE voltage you will do a lot of damage. Now what I am saying is the two switchs PTO and Clutch has both postive and negative going through then. As far as I know a negative turns off the mower engine.

This has nothing to do with this thread, but I feel that I have to answer the last post. Positive and negative voltage only comes into play in an AC (Alternative Current) circuit. In this type of circuit you will have both voltages because the electrical wave will go above and below the median line, caused by the alternate magnetic poles used to produce it. When this type of current goes through a voltage rectifier or regulator it is converted to DC current, the negative voltage is flipped to the positive side of the median line. In a DC circuit you will have only one voltage, positive.

Secondly, if you look at the schematic carefully you will see that the PTO and Clutch switches are really two switches in one. Those connected to the orange wires are NO switches and used only in the starting circuit. Once the engine is started the key is released and the current will start flowing through the switches which are connected by the yellow wires, which are part of the run circuit.

Again I repeat that this reply has nothing to do and does not pertain to this thread.

Ok, we know that the switch is the correct one. Let's go to the first test. Make sure that the fuse is good. You will need to put some weight on the seat to close the seat safety switch. Put the brake/clutch pedal in the down position and apply the parking brake. Raise the deck to the highest positions. If I remember this unit correctly, raising the deck also sets the parking brake. Hope I am right, but is does not matter. Use a test light if you have one for this test. If you don't have one, you can use the multi-meter as a test light by setting it to 20V DC and connecting the ground lead to the negative terminal of the battery. With the key in the start position check for 12+V at the small terminal of the solenoid. If you have 12V your starter should kick in. If not we start back tracking to the key switch. How??? In this order, follow the orange wire back to the PTO switch and test both orange terminals for 12V. Follow the orange wire back to the brake switch and again check for 12V. Follow the orange wire back to terminal #5 (S) of the key switch and check for 12V. Post results and we will continue.

Click to expand...

I had done this check several times previously and gotten 0 V. Then earlier today I started getting 12V at the solenoid small wire. I tried this again as you asked and noticed the voltage coming and going. Out of curiosity I tried lowering and raising the deck while measuring voltage(and also did a continuity check) and saw same thing - voltages there then not there -and it seemed to be making it worse. Naturally I suspected a loose connection. As I had mentioned before when checking the PTO switch and harness I found what looked like extra wires, taped outside of the factory shrink sleeve of the wiring bundle and tying into the back of the PTO and brake switch harness. One was orange the other was blue which matched nothing on the schematic, and were a smaller gauge wire. They followed the regular wiring down to the brake switch. I checked the PTO switch itself and it's doing what it's supposed to. I put the test leads inside the PTO switch harness and with some jostling I got the the same short, then open readings. I had to call it a day at that point but will have a closer look early tomorrow. Think someone could have been trying to bypass the safety switches? Whatever the case, there's a connection issue in the PTO harness that's causing shorts and opens without the switch involved, which would seem to explain the voltage readings coming and going.

Ok, I understand, am going to shut down also. I would remove those extra wires and going through the tests, just to see what happens. I'll watch for your post tomorrow. Be in and out all day, but will continue to try to help.

MTD, I just found a problem. I have a few others tracking this thread to make sure that we are doing things right. They are contacting me, instead of posting, to keep things from getting to confusing. One of them just pointed out to me that in your post on the key switches, you have the wires going to the B & S terminals reversed. The two red wires need to go to the B terminal, top right and the two orange wires should go to the S terminal, bottom left. That would explain many of the problems. Sorry I gave you the wrong info.

Rivets said:

MTD, I just found a problem. I have a few others tracking this thread to make sure that we are doing things right. They are contacting me, instead of posting, to keep things from getting to confusing. One of them just pointed out to me that in your post on the key switches, you have the wires going to the B & S terminals reversed. The two red wires need to go to the B terminal, top right and the two orange wires should go to the S terminal, bottom left. That would explain many of the problems. Sorry I gave you the wrong info.

Click to expand...

The answer to that would actually be a whole other question of interest although it is related to the post. I'll try to explain as best I can hopefully without creating another fork in the road. The original switch shown in the pic is in fact the reverse of the new switch, in just the ways you describe - B & S terminals reversed. The Lights (L) & Aux (X) are also reversed in the same manner. I have not attempted anything with the new switch. I was hesitant because of the reversed terminals. I think this is a good question of general interest since this was sold to me by a Murray authorized lawn repair service as a factory part replacement for my model . The question being whether those two switches are 100% compatible. But I didn't bring that up because I thought it would complicate things more.

So, to be clear, all of my troubleshooting has been with the original switch which is wired as I described above. And since the mower ran fine before I am assuming that all is well with the way the original switch was wired. The original switch has no clear Letter markings like the new one and even with a magnifying glass I could not find any letters on the old switch, which was kind of aggravating in itself.



Update:

I was able to perform the same continuity and voltage checks I did yesterday and got the same results, which was:

Seat occupied, brake pedal depressed, and deck up (so all safety switches are now closed and ready for START) I checked both voltage and continuity from the ORG wire on the ignition switch to the small ORG solenoid wire. What happens for both is that I'm getting intermittent readings - OPEN to SHORT. I then lowered to deck (blade engage) and same thing. In other words, I could not get the meter to read OPEN (when the deck was lowered) & SHORT (when the deck was up in START position) like it should. I noticed that raising and lowering the deck seemed to aggravate the situation - made it go from OPEN to SHORT on the meter. I also reached my hand in and jostled the PTO switch & harness and it caused the same type behavior. I haven't had time to figure out what those extra wires are for. I'll have to put the mower up on ramps and crawl underneath to get better access. I'll be out for work the next two days and probably won't be able to get to it until Sat or Sun. I went ahead and ordered a new PTO switch assembly in case that's what the problem is.

Does this sound like a switch or harness problem? I checked the physical position of the PTO switch and the deck lever looks like it's making good contact to the button.

Back to square 1, we have to check the switch to see if both of them act the same way. With you multi-meter, connect across the B terminal and the S terminal. Turn the key to the start position. You should have continuity. Releasing the key to the run position, your meter should read infinity. Next connect the meter across the B terminal and the M terminal. Turn the key to the start position. You should have continuity. Releasing the key to the run position, your meter should still read continuity. Do this on both switches, to make sure they are the same. Report back what you find when you get a chance.

One other thing. It gets very confusing when you report back things that I do not request. Remember, that I have to visualize what is happening and when I have to read two or three different things it is very easy to make mistakes and jump to conclusions. That's why I told you my methods are crazy, if I were there to see what was happening this problem would hav been solved by post #10. Sorry but that is the way I am, I warned you.

In a DC circuit you will have only one voltage, positive.


I will sure disagree with this. I repaired DC electric fork trucks for over 11 years and if you don't know what negative voltage is you will be way over your head fast and it best not go to the chassis. Gas powered equipment just uses the chassis for most of the negative side is the only difference. Has to make a circle back to the battery somehow. Even your house AC current makes this circle all the way back to the power company I think it cycles back and forth 60 times a minute or something like that. I really don't know that much about AC.

Result # 1 - for NEW SWITCH

connect across the B terminal and the S terminal.

Click to expand...

This gives continuity in START ONLY, then reads open in RUN. Just as you described

Next connect the meter across the B terminal and the M

Click to expand...

Turn the key to the start position. You should have continuity

Click to expand...

This gives NO CONTINUITY when key is turned to START or RUN

***Wondering if you meant to specify two different terminals here? - would this not put full cranking voltage on the magneto? Did you mean NO continuity between B & M?


Result #2 - for ORIGINAL SWITCH

B to S gives continuity with key in START, OPEN when released to RUN

B to M gives OPEN in START & RUN (same as for the NEW switch)

Ok, that should be good, Let's do a couple of more. B terminal to L terminal. Off position no continuity, run position continuity. S terminal to L terminal. Off position no continuity, run position no continuity. M terminal to G terminal, run position no continuity, off position continuity.

Also, please check to see if you have continuity between the L and X terminals both in the run and off positions. I am trying to find out why the schematic drawing is not consistent with the way you say the key switch is wired. FYI, Going to be in and out all day so I don't know when I'll be checking in.

Rivets said:

Ok, that should be good, Let's do a couple of more. B terminal to L terminal. Off position no continuity, run position continuity. S terminal to L terminal. Off position no continuity, run position no continuity. M terminal to G terminal, run position no continuity, off position continuity.

Click to expand...

NEW SWITCH

B to L: OFF gives No Continuity, RUN gives No Continuity

S to L: OFF gives No Continuity, RUN gives No Continuity

M to G: OFF gives Continuity, RUN gives No Continuity



ORIGINAL SWITCH


B to L: OFF gives No Continuity, RUN gives No Continuity

S to L: OFF gives No Continuity, RUN gives No Continuity

M to G: OFF gives Continuity, RUN gives No Continuity

Rivets said:

Also, please check to see if you have continuity between the L and X terminals both in the run and off positions. I am trying to find out why the schematic drawing is not consistent with the way you say the key switch is wired. FYI, Going to be in and out all day so I don't know when I'll be checking in.

Click to expand...

NEW SWITCH


L to X: OFF: No Continuity, RUN: No Continuity

*** I know you didn't ask for this but L to X gives Continuity in the LIGHTS position. The positions of this switch are: OFF, LIGHTS, RUN, START



ORIGINAL SWITCH:

L to X: OFF: No Continuity, RUN: No Continuity

LIGHTS: Continuity




I'm not seeing what is different between the drawing and the way the switch is wired. The wire colors match exactly.

Something's not right. In post #59 you said top right you had orange wires and bottom left you had red wires. In post #62 you show top right as battery terminal and bottom left as solenoid terminal. In the schematic red wires should go to battery terminal and orange wires should be connected to the solenoid terminal. Do you see the difference I am seeing? As I see it the engine will only turn over with the deck down and foot off the brake petal.

Rivets said:

Something's not right. In post #59 you said top right you had orange wires and bottom left you had red wires. In post #62 you show top right as battery terminal and bottom left as solenoid terminal. In the schematic red wires should go to battery terminal and orange wires should be connected to the solenoid terminal. Do you see the difference I am seeing? As I see it the engine will only turn over with the deck down and foot off the brake petal.

Click to expand...

Ok, I think what you are seeing is the difference between the two switches - the original switch & the new switch (which I have not used). What I said is correct, the original switch has B (red wire from battery) at bottom left and S (org wire from solenoid) at top right. The NEW switch has the B and S in reverse positions (as well as the L & X).

Stated another way, if you look at the factory schematic, the original switch in my mower matches the schematic exactly - red wire goes to bottom left & org wire goes to top right. (white wire goes to top left & vio wire goes to bottom right).

I had thought the same thing you did - that the schematic made it look like the mower would only start with deck down. What I know for sure is that the original switch is wired as I stated above and before it broke the mower only started with the deck UP.

**As to the difference between the two switches, the only thing I can think of is that the switch for the B and S is a simple single throw type and only requires an ON/OFF connection, meaning that it apparently doesn't matter whether B or S is top right or bottom left so long as they are limited to those two positions. Either that or the NEW switch simply isn't compatible with my mower. That's why I never tried putting the new switch in. But since the original switch was tested out of circuit and tests good it shouldn't be an issue.

I understand what you are saying, but all the tests I asked you to do have come back with the same results for both switches. That is the problem for me. When testing electrical circuits you can NEVER ASSUME ANYTHING. I still believe the two switches are the same. There are many different types of six terminal switches, some know as simple ( meaning connecting two terminals at a time ) and others known as complex ( means multiple terminal connections ). I am trying to find out what type you have by the picture and what you tell me. I am going to be unavailable until later this evening. You might try to install the old switch back in and go the the electrical procedure I posted earlier and see what happens.

Any new's, update's on this one...?

I installed a new PTO safety switch and harness assembly. Everything now reads as it should and, finally the mower cranks again!

Best I could tell, someone had previously either tried to fix the problem with auxiliary wiring or had attempted to bypass the safety switches.

Thanks again to everyone for their help & support ! :thumbsup:

Well done to you, you made it...:thumbsup: hope now you have many happy hours mover....:smile:

Its been a long road, but you got there.

Thanks EngineMan. I'm just glad to have a working mower again. :smile:

Yes am sure you are..! just like a woman, they need a little TLC sometimes...:laughing: