Electrical woes...

[aprophet2]

Hi All. I just got done cleaning up a bad mouse infestation in my old Toro lx500. They chewed one of the plug wires in half and a lot of the insulation on the white kill wire that runs between the two coils leaving a fair amount of exposed wire. I replaced both coils and replaced the section of white kill wire that was damaged. Now the machine will start right up and runs great if that kill wire is disconnected from the second (or both) coils but of course, in this condition the mower continues to run even if you get off the seat. That's super dangerous IMO and I'd like to make it work correctly. If I plug the white kill wire back into both coils it will not start. I've checked the 20A fuse and cleaned the seat switch (which is really just a spring steel contact) but I'm not sure where to go next. I have a multi-meter and a base understanding of how to use it but these types of electrical issues do tend to vex me. Any help or suggestions of next troubleshooting steps would be welcome and appreciated. Thanks!

 

[StarTech]

Please post the engine info. It depends on the engine setup. Some have a pair of diodes in that wiring harness, others the diodes are in the coils. But with you replacing both coils, the diodes may have been the section that was replaced or you still have an electrical short in the kill circuit somewhere.

 

[Rivets]

I would start by tracing the kill wire from the coil back to the switch. This is a problem all of us who work on electrical problems hate as it is slow and tedious. Patience and a friend will be of some help, as you are looking for a place where the insulation is rubbed through or bad connections. Number one rule when working with electricity, DOUBLE CHECK EVERYTHING AND DON’T ASSUME ANYTHING.

 

[StarTech]

Number one rule when working with electricity, DOUBLE CHECK EVERYTHING AND DON’T ASSUME ANYTHING.

How True..

 

[aprophet2]

Hey Guys. Thanks for the replies. The engine is a Kohler SV720 (23 hp Courage) I'm OK with the tedium and I'll get it done but to be honest I'm not really sure exactly how to trace that kill wire back to the switch, or which switch is even in question here. If anybody has the time/patience for a little more specific direction I'll get out in the driveway and try again tonight (in the snow) because this is starting to make me nuts!...

 

[StarTech]

Okay this engine's coils have the steering diode built-in the coils. There are two safety switches involved the seat and brake. Both are required to be depressed to prevent the engine kill function. According to wiring diagram you would tracing the yellow from the engine back to the ignition switch. It also goes to the brake switch. Then it continues as a yellow wire with white tracer to the seat switch. There also a yellow wire from the seat switch to RMC module.

Wiring info service manual. Your mower wiring is near back of the manual.
https://www.toro.com/getpub/38101

 

[Rivets]

Here is a manual which will help you out. Has a wiring diagram of your unit and will give you a better understanding of how you systems work. I know I shouldn’t do this, but I’m assuming you have a VOM and know how to use it. The switch I’m talking about is the key switch. With the key in the run position, PTO switch OFF, and the seat switch closed, you should get zero continuity between between the kill wire and ground. Remove kill wire from coil to test this. If your engine dies while in use, some where in this circuit you have a short to ground, killing the engine. That short is what you are looking for. https://www.toro.com/getpub/34847

Looks like Star beat me to it.

 

[StarTech]

Just trying something here as the redirect isn't working for me Rivets.

Test link

EDIT: aHHH I see the problem it is adding HTTPS to my links and my Firefox setup don't like it. Oh well Internet Explorer works.

 

[bertsmobile1]

When working on the kill wire I like to use a test lamp with the clamp on the + side of the battery because you are looking for a short to ground.
Always pull the kill wires off the coils because as little as 9V dc at 0,01Ma will fry most f the control circuits in the trigger chip.
Next thing to do is make up a 1/2 dozen patch wires with a male spade at each end so you can jump all of the safety switches .
Having done that if you still have a ground short you are looking at a bare wire & not a defective switch .
Over the ( few ) years I have been doing this most times it is a wiring short & not a bad switch.
This of course assumes you can work out which switches are open or closed in the run position.
IF you are confused the ask as we all have the same diagrams at our disposal ( thank you Toro )

 

[aprophet2]

OK fellas. Those Toro guides are great stuff. At this point I've checked all the switches and searched thoroughly for bare wires and I can say I'm 99% sure that they're good. It still won't start with the white kill wires hooked up to the spade terminals on the coils. But....As a test I hooked up the kill wire on the second coil only and it will start (the machine actually runs great but for this electrical problem). Interestingly when get off the seat while it's running I can clearly hear that left cylinder cut out (even thought the engine is remains running). So that kill wire / safety switches are working as they should on the second coil but when the first coil (right hand side) is hooked up to the kill wire it will not start. Could that right coil be bad somehow - even though it runs fine without the kill wire? It occurs to me now that I should have mentioned this; these new coils are not OEM from Kohler but Chinese parts from Amazon. For what it's worth; I'm thinking the problem may be with the coil now based on the above test and Bert's statement :
"Always pull the kill wires off the coils because as little as 9V dc at 0,01Ma will fry most f the control circuits in the trigger chip."
which, I'll be honest, I don't fully understand but I get it enough to know that I've been screwing around with this thing for days and maybe I could have inadvertently done some damage to the coil... Thanks for sticking with me here!