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Discussion Starter · #1 ·
John Deere 420 was running fine when I pulled it out of the barn, Got off the tractor to shut the barn door, got back on to go and moved the travel lever out of neutral and the engine died. The engine restarts fine and runs, but once the lever is moved it will die. I have noted that the battery light is on all the time. I thought possibly the seat safety switch jumper that I installed some time back was bad, but have check and rechecked it numerous times and it appears ok. I and getting a ground reading on one of the wires leading from the seat safety switch. Took the seat tub off today and there does not appear to be any spots on the wiring from the seat to the engine compartment where the wire could be going to ground. I have a wiring diagram and can trace the seat wiring, I am getting a very strong ground reading on the wire from the fuse cartridge to what appears to be the Time Delay Control box. The wiring diagram that I have does show the dash amp light controlled from the TDCB. Is my problem in the TDCB, the neutral safety switch, seat safety wiring, etc.? Any help is welcomed. Thank You.
 

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I agree with Drew.

On the other issue (ground reading on one of the wires leading from the seat safety switch) are you checking this with the TDCM connected or disconnected? There is a ground connected with the TDCM and you could be getting the reading from that.
 

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Discussion Starter · #5 ·
Seat Safety Switch

Check your seat switch and related wiring to it.
The seat safety switch was jumpered out at least ten years ago. I have re-jumpered it twice the same way and still have the problem. I appreciate any ideas that you have. There has to be something that I am missing. Could the TCDM be interfering? I had a dealer tell me no but then again, he is trying to sell me a new unit. Thanks everyone.
 

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The TDCM is not the issue in almost all of the instances of engine dying when the ground speed lever is moved out of neutral, but rather the safety wiring systems around the TDCM that provide input signals to it.

The first thing to check is the F2 fuse that provides voltage through the seat switch (or a hacked harness with a jumper around the switch...) to the control pin of the TDCM. If that fuse is blown, the wires leading back to the switch location may be shorting against the tractor frame at some place along the path -- was the fender deck recently removed and then reinstalled on this tractor?

You might find this summary of how the TDCM module works -- particularly with regard to the ignition interlock -- a useful document to review:
https://www.wfmachines.com/forums/showthread.php/97553-TDCM-voltage-measurements-and-what-they-mean

Chuck
 

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Discussion Starter · #10 ·
I thought that I should let everyone know what happened as we learn from each other. First off, Chuck nailed it, the F2 fuse was blown. Upon further inspection of the wiring, there was no short to frame so how did this happen. Well, John wired in the seat jumper about ten years ago and the resulting wiring was sticking out the hole on the frame in back of the seat. He put his metal pull chain behind the seat on the jumper and it went to ground. So here is a situation where the tractor had a blown fuse due to external forces. Interesting? The old girl is working great! Thanks again! SkeeterJo
 
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