Need Help with troubleshooting ignition switch on Murray 12.5 HP

[MTD]

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

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?

 

[EngineMan]

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.

 

[MTD]

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.

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.

 

[Rivets]

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.

 

[EngineMan]

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....!

 

[MTD]

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.

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?

 

[Rivets]

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.

 

[Rivets]

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.

 

[MTD]

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.

 

[reynoldston]

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.