425 will not shut off

[oldnslo]

Good friend has a 425 that will not shut off unless we disconnect the battery cables. We have tried disconnecting the ignition switch with no change. When you touch the battery terminal their is a spark and an audible click almost like the starter solenoid but it isn't.

Any suggestions on where to start looking or where to get an electrical diagram for this machine.

TIA

Roy

 

[beenthere]

Does it start up normal when reconnecting the battery cables?

I'd suspect a faulty ignition module. or maybe the ignition module.

A tech manual is available on CD or booklet that will give the wiring diagram.

A portion of the system operation dialogue. See the 4th line down.

 

[oldnslo]

Thanks beenthere,
I suspected their was a relay being powered up when we connected the battery but wasn't sure what it was for. Will have to see if the local dealer will give us a peak at the wiring diagram or not.

Yes it starts and runs fine, it just won't shut down even with the PTO engaged and you get off the seat. I am 99.99% sure it is an electrical issue but where to start looking is the $64 question.

Roy

 

[beenthere]

Which part of the diagram do you want to peek at? Here is the ignition schematic up to s/n 070,000

 

[oldnslo]

Thanks been there, looks like that schematic shows the start circuit with all of the safety switches. Just have to start chasing wires and see if we can determine what component is faulty.

Roy

 

[beenthere]

Is the s/n above or below that 70,000? That is mfg before '99

Maybe you will find a loose wire or connection. Seems starting at the ignition switch as turning it off should start a chain reaction that shuts down the engine. There are a number of troubleshooting items, none of which specifically addressed the engine not shutting down. Only start-up and running problems.

 

[beenthere]

If below 70,000 then this shot of the component locations may help. A1 is the Ignition Delay Module and A2 is the Ignition module located on the engine. I'd start with wiggling the components and wire connectors leading to them while key off and engine still running.

 

[oldnslo]

thanks beenthere,
s/n is in the 40,000 so this info is greatly appreciated. Friend is out of town on family business but thought he would be back tomorrow. If not I will probably take my BX over and mow his hayfield/ lawn.

Roy

 

[Greenblood2011]

Look for the diode by the ignition relay, it's probaly bad. That diode stops power from backfeeding the relay causing it to stay on. It's shown in the wire diagram. Good luck

 

[beenthere]

Greenblood2011

Sounds like you are onto the possible problem.
Would the ignition LED (lit or unlit) on the control board be a clue to a bad diode?

Is the location of that diode shown in the tech manual? Or just trace it along the 706 pink/black wire shown in the schematic.

This is what the tech manual says about tracing the signal through the ignition relay (doesn't point out the diode tho).

With the operator off the seat and the key switch in the
run position, current flows from key switch terminal B to
terminal A, power fuse (F4), ignition relay terminal 87,
brake switch (S3) (brake pedal depressed), PTO switch
(S4) (PTO disengaged), ignition relay coil terminal 85, <<--( diode here)
and ignition LED(E1). The ignition LED indicates that
power is available to the ignition relay coil. With the
ignition relay energized, current (C) flows to the PTO
switch, and ignition delay module. The ignition delay
module allows........