John Deere 400G Wiring Diagram

My Dad has a 1989 model John Deere 400G he bought this spring. He changed oil on it this week, started it afterwards, and then it wouldn't start again. A couple days went by and he still couldn't so I went out last night and looked at it and troubleshooted it best I could, everything seemed to check out, and I looked at JD parts before hand.

Had power to the starter solenoid and the starter relay checked out, so I pulled the dash and found a mouse nest and can see three wires have been chewed on with bare copper showing.

Dad is willing to buy the manual, as I said that would come in handy to see the wiring diagram. In looking it up there is TM1411 and TM1412. One is the 'Test' manual, the other the 'Service' manual. Which one has the diagrams I want? I hope splicing the wires gets it going, but I hate to get them fixed and still not have power to the dash. At the point the diagram would help me troubleshoot through the different circuit breakers and such.

If anyone can help me out with what manual to purchase I will download it and print out the pages I need as I hope to work on it Saturday, or if someone with the manual would send me the pages that would be great too.

At this point with the key on there is no power to the lights so need to get that fixed and go from there.

Also does anyone know, that bulk head connector, at the firewall, does that unscrew and come apart? If so I could do so then work on the wires easier, if not will have to work inside the dash area. Thanks!!

I can't say for sure on the 400G, but I looked at my 450E manuals and the operation and test manual has more info on the electrical system and components than the repair manual. Some diagrams but a lot of info on wire colors, locations in connectors, etc. As a guess I would say the test manual first but I recommend getting both. I got the downloads from john Deere Technical Publications and print things as I need them, less expensive than printed or disc copies.

I doubt if any manual will help with your problem,what I would do is get my soldering iron on,a packet of those shrink sleeves,make myself comfortable and sort out each wire one by one,either join them as they are if long enough or add in a new piece as needed,I've had a few burn outs in my time and that's how I done it,there is an online site tradebit.com that sells PDF manuals you could have a look there.
AJ

I went ahead and bought TM1411 on ebay, as in looking I see it has the big fold out wiring diagram with the wires labeled as they are on the actual wires.

Also it tells how to test each circuit, charging, relays, circuit breakers, test the batteries, etc. That's what worries me the most, is not fixing the wires, but if I do and then still nothing. From there I want to be able to go through and troubleshoot with a test light/multi meter and be able to find the problem, not just throw parts at it.

One of the wires chewed on goes to the main relay/power supply mounted on the firewall, so I'm thinking that there is the problem. Yet want to make sure I'm getting power to ignition switch after and what each lead does in case something shorted out.

Thanks for the help both of you, hopefully I can fix the problem and he can get it moved in the shed so it's out of the way again, and if it dries up do some work with it.

I got the dozer going last night finally. Will reply in hopes if someone in the future has trouble they can read what the fix was.

I received the manual I was suggest (thanks for that) and it was a huge help, showing the wiring and many other various readings and tests.

I next took the wiring harness from the bulkhead connector at the firewall out so I could take it home and work on it. I soldered and shrink wrapped the 3 wires that were chewed on. Two were coming out of the bulkhead connector harness, the other one chewed on was the red going into the logic module.

Putting it all back together, and nothing. I did the tests in the book, shorting out lights see if they light on the dash, and they did. I feared it was the logic module and somehow it shorted and it was bad. Being $500 I hoped not but suspected it might be. I went out the next night to look some more and found putting the harness onto the ignition switch a terminal was off, so put that back on and I did have some lights, but dozer would not start.

Testing the ignition switch I thought it was bad while up in the shed. But in testing it in the house in better lighting I could see the small print better and it seemed to test good, yet seemed finicky. I sent the harness of to be checked, which is was, and tested out good, but they also said they suspect the switch.

Ordered a new ignition switch, put it all back together last night, and turned the key on, got lights, but didn't turn engine over. Moved transmission lever a little bit and off it went! I really think when dad said it takes lots of moving the lever around until it starts it was in the switch. Makes sense switch was going bad, just happened he did some maintenance on it and that's when it chose not to start. And then that I kept troubleshooting it and found where the mice chewed on the wires and I figured it was that, when it was really the combination of the two probably.

It can now get put away for the winter tomorrow, and we can move rest of tractors around as well. Next spring plan to re-wire the lights for him and get the horn going for him also.

Thanks for the help and the suggestions!