starting/electrical problem JD 5420

galazzo · May 9, 2011

When I try to start my JD5420, I turn the key on and blow the 20 amp "key switch" fuse. I removed the key switch and will have it tested tomorrow but I'm thinking problem may be some goofy "saftey" switch.

Any ideas?

Just Bill · May 9, 2011

If it is happening as soon as you turn the key on without trying to start it,
it sounds like you have a wire shorted to ground.
It may be a bad spot in the insulation from rubbing or it might be pinched.
I would check the wiring first.

JD5210 · May 9, 2011

I believe the problem is the temperature sensor. On the thermostat housing there is a temperature sensor that is connected to a two wire harness that goes to the injection pump, this is the "cold start advance" portion of the system so it starts easier when cold, the sensor is so it doesn't activate once warmed up. If you disconnect the sensor and it works fine ohm the sensor, probably shorted.

The sensor on the thermostat housing, that controls the advance on the inj. pump. When it fails it shorts out and blows the fuse. Try unplugging it and see if it starts and runs. I thing the part # is RE503242, (JD parts URL include) if you are quick changing it, you don't have to drain the coolant, just make sure it's not hot at the time.

I have included a picture, it is item #2

John Deere - Parts Catalog

galazzo · May 9, 2011

JD5210 YOU ARE THE MAN!! That was the problem, tractor is up and running with sensor unplugged. The part is ordered. If you make it out to OR look me up, I owe you a six pack.