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Read articles →This is a narrow, problem-specific repair video, not a tractor overview: an owner walks through diagnosing a no-start issue on John Deere 4200/4300/4400 tractors caused by a failed thermistor behind the fuse box, gives the replacement part number, and shows his own workaround of wiring in an aftermarket marine horn button as a permanent bypass. Useful for owners with this exact no-start symptom, not general shoppers.
Posted by an owner sharing a hands-on fix from his own tractor and property, not a dealer or professional technician.
A failed thermistor behind the fuse box breaks the circuit after the solenoid, so the starter keeps cranking but the tractor never gets that final crank over to start.
The part number referenced is LVU10323, described as a cheap part costing about a buck ninety-eight.
Yes, wire in an aftermarket marine horn button as a bypass, about $8 from Amazon plus some wire and soldering, so you never deal with it again.
Press the horn button first, then turn the key. You cannot turn the key first; you must press the button, then turn it to start.
