Need Help with troubleshooting ignition switch on Murray 12.5 HP

[reynoldston]

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.

 

[MTD]

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.

 

[reynoldston]

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.

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.

 

[reynoldston]

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.

 

[MTD]

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

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??

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.

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.

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.

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.

Ok. Did as advised and it turns over.

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) ?

And for the current post, in answer to questions:

From post #28

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

From post #23

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

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.

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!

 

[EngineMan]

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.

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...!

 

[reynoldston]

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.

 

[MTD]

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.

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.

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?

 

[EngineMan]

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.

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.

 

[MTD]

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.