JD 420 garden tractor quit/wont start

[tshell]

Have a late '80's John Deere 420, Onan engine, and all of a sudden the battery light came on, next the mower deck stopped. When I put it in forward (hydro) it began to die. To get it back to the house I held a stick against the neutral interlock switch next to the drive lever. Got it to the garage and jumped the wires to take the switch out of the loop. Started up the street to my neighbors house to have him look at it and it just died. I took the battery out and cleaned it up and tested it, ok. Stuck it back in, and it wont even turn over or click. Could it be the ignition switch or is there some electronic ignition module that could be bad? Anyone familiar with this problem? Nothing in the manual. The tractor is in great shape, I try to take care of it. 60" mower deck.

 

[JerryK]

Have a late '80's John Deere 420, Onan engine, and all of a sudden the battery light came on, next the mower deck stopped. When I put it in forward (hydro) it began to die. To get it back to the house I held a stick against the neutral interlock switch next to the drive lever. Got it to the garage and jumped the wires to take the switch out of the loop. Started up the street to my neighbors house to have him look at it and it just died. I took the battery out and cleaned it up and tested it, ok. Stuck it back in, and it wont even turn over or click. Could it be the ignition switch or is there some electronic ignition module that could be bad? Anyone familiar with this problem? Nothing in the manual. The tractor is in great shape, I try to take care of it. 60" mower deck.

There is a control module. I have an '91, and mine is mounted on the steering colume. If you open up the hood and look down right behind the dash...you will see a black plastic box..that is the box with the control circuits in it. You have to take the battery out and the battery pan to get to it proper. There is an electronic module behind the flywheel that goes bad, but that just keeps the coil from firing...usually goes bad after the motor heats up a little. But your problem is probably the fuse or fuse holder that is right above the control module. I think it is a 20 amp, and should be right in plain sight up at the top. Wiggle this fuse...and I bet your problem fixes itself. You probably have to replace this fuse holder and put a shinny new fuse in it....and you will be good for a long time. The fuse holder gets crud/water in it over time and causes problems. This is all from experience....been there....done that.... The switch on the HST forward/reverse only keeps it from starting... The 420 is an excellent tractor...about 1000 pounds and built to last. If you ever have to pull the Onan to replace that spark pickup, put you a new starter in it whilst you have it out.

 

[tshell]

Thanks, I had just replaced the 20 amp fuse before I saw your post, and it fired right up. When I went to go forward (and still have the neutral safety switch jumped out) it blew right away again. I have a bunch of 20 a fuses, but no sense in keep changing them...?

 

[JerryK]

Maybe your jumper is shorting something to ground. I'd take it out...and see. If it still blows, you can pull the control module, then get your manual/electrical print out and see what is shorted. I have never had trouble with the control circuit...but took it all apart once just checking stuff out when I was working on something else.. Good luck..!!!!

 

[JerryK]

Forgot...there is also a regulator module mounted on the top right of the Onan...just to the right of the carb. I think it has three terminals on it.... Can't remember if I have ever had trouble with that one....but that's it for electronic stuff......

 

[tshell]

I called the local JD dealer today, they supposedly have a tech that is good on these, and he was kind enough to talk to me. He told me it would be rare for the control module to go and it would not act like that (he called it the time delay safety module). Also said the capacitor or voltage regulator or ignition switch likely wouldnt do this. He said it sounded like some wire somewhere going to ground. Thats why the tractor stalls and fuses keep blowing (but only when I try to go forward or hit the PTO clutch switch??). SO I guess I'm in for some electrical snooping to find a ground. Does that sound right?

 

[JerryK]

Anything is possible. There is nothing electrical about moving the HST lever to go forward or reverse except the 'neutral' switch. May have worn thru some of the wiring that runs in that area under the dash [ most of the wiring goes to the control module that is right next to the HST control lever], or somewhere else. With the years of use we have gotten out of these tractors...who knows. Do you have the repair manual with the wiring diagram???

 

[tshell]

Nope I do not, should have gotten one somewhere I guess. My guess is to try the neutral, PTO, and seat switches, and then the PTO clutch itself. Bought with about 450 hours in 1989, used from a golf course that closed, he just trimmed with it, and now it has 900 hours. And the grass just keeps growin'.

 

[JerryK]

Here is a link to the wiring diagram... Again, your first problems sounded like the 20 amp fuse was loosing connection...and I would check out that fuse holder real well. That is what went bad on mine.. Also, since you stated that you got it home by sticking something in by the neutral swich...I would check that area for a worn thru wire... Good luck...

http://www.weekendfreedommachines.com/discus/messages/335/316_318_420_wiring-257536.pdf

 

[tshell]

Many Thanks, you are a tractor guru...I'm off with my test lite and meter............