JD 425 cranks with key in on position.

[ILENGINE]

This one has me puzzled. Engine starts cranking as soon as the key is switched to the on position. New JD key switch/circuit board. Older below 70,000 serial number unit. Start wire is getting power at the circuit board X1 pin 5 with no crossover power between any of the other wires connected to the circuit board. So something is triggering the start relay on the circuit board. Old key switch/circuit board has same symptom.

 

[Mark H_NO]

Is the relay stuck?

 

[ILENGINE]

Is the relay stuck?

No. Appears to be on the control side of the circuit board wiring that is closing the start relay.

 

[slomo]

Find out where the short is and fix it. Go wire by wire ciruit x circuit.

 

[Mark H_NO]

You said the old circuit board/switch did the same thing, gotta be in the wiring.

 

[slomo]

You said the old circuit board/switch did the same thing, gotta be in the wiring.

Unless it is a coincidence same part failure on the new part. Total shot in the dark.

Still think there is some wire issue too.

 

[StarTech]

I assume you mean 425 and not the Z425.

Ground circuit problem with starter relay.

 

[ILENGINE]

Unless it is a coincidence same part failure on the new part. Total shot in the dark.

Still think there is some wire issue too.

I am thinking the same. Some wire is crossing over inside of the loom.

 

[ILENGINE]

I assume you mean 425 and not the Z425.

Ground circuit problem with starter relay.
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View attachment 74437

Engine will even crank with the seat switch, pto switch, and brake switch unplugged. just have to turn key to on position. Not even start. Disconnecting X2 connector at circuit board will stop the crank cycle. Also appears to not have key power to the ignition delay module, the ignitor, or the fuel pump

 

[Auto Doc's]

If I am not mistaken these had a square red box style plug in diode that would go bad and create a circuit feedback issue. Locate the diode under the control panel and unplug it to see if that corrects the issue.