Electrical problem??

[mx125]

Tractor running fine. After approx 2 hours i shut off and got no crank on restart. No lights either . .just a weak whine behind the instrument panel. Thought maybe alternator died and somehow battery drained (but how with no lights running??). Tried boosting from truck . . got lights but weak crank. Two hours later tried again with jump . .still weak crank but started. Once running, glow plug light stays on at high rpm and all three dash lights flicker at low rpm. I hear the glow plug click on and then off after 3 seconds when i turn ignition on so seeems to be a mysteery light only. Also get no headlights or flashers. Without boost i get absolutely nothing.

So . . thought perhaps bad ground . .or loose battery terminals. However with truck clipped to the battery cables issue still present.

Grond wire from batt looks and feels solid. How do I check that? Or . . is it possibly a relay that can be partially overcome when I attach the second battery? Or is it a myterious computer controller that I can't trace?

I should mention that I don't know how to actually test a relay!

Thanks in advance. Dealer can only suggest weak battery connection . . and would prefer I trailer it an hour into their shop.

 

[High Compression]

I had a similar issue once. Turned out to be the ground cable was bad. Best way to check it is to unhook it from both ends and then put a multi-meter on it and check for your resistance. You should have zero. If you read any ohms at all replace it. It might look fine but the meter will tell. Same for the pos. cable. Hope this helps.

 

[mx125]

Thanks for the quick response. Il definitely give it a try. And I suppose the cable is simply the line from the battery to the side of the frame? I wasn't sure if there were other electrical to frame wires I needed to check. Thanks.

 

[High Compression]

There might be another ground, but most tractor engines are not rubber isolated like car engines so they typically don't have another main grounding cable and the engine/chassis grounds don't generally go bad. The battery cables take the most abuse by the load that is put on them. BTW the way I test a relay, is to replace it. If it doesn't change anything it's probably still good.

 

[greg_g]

Clean the battery ground cable at both ends. Follow it to where it bolts to the frame, remove the bolt, grind down to bare metal. Put some dielectric grease on the clean spot, bolt the cable back on, paint over if you wish.

If that doesn't resolve your issue, next step I'd recommend is to isolate the glow plug circuit from the electrical system. In some cases it's as simple as pulling a fuse, but the most positive method is to disconnect the feed wire.

//greg//

 

[mx125]

Thanks Greg D. I will do all of the above this weekend. It would be great if it was simply a bad ground! In your experience, would a bad ground cause all of the things I mentioned, including a mystery glow plug light?

If it is a glow plug loose connection . . .that makes me wonder why it would affect ather things. Fingers crossed for the bad ground.

Also, I suppose I should pick up a relay and try the swap that 'high compression' mentioned, if your grounding advice doesn't turn up the issue?

A few follow-ups if I may:
-Are all the relays the same part?
-Is there a laymans wiring/parts diagram somewhere short of buying a service manual? (if those exist)
-Is there a computer or contoller unit that could be the ultimate culprit or are these tractors not that sophisticated?

 

[High Compression]

Some relays are 4 pin and some are 5 pin. Best thing would be to remove yours and go match it up. Try: John Deere - Parts Catalog and type in your model at the upper left corner. Then use the alphabetical index to find the wiring diagram your looking for.

 

[mx125]

Some relays are 4 pin and some are 5 pin. Best thing would be to remove yours and go match it up. Try: John Deere - Parts Catalog and type in your model at the upper left corner. Then use the alphabetical index to find the wiring diagram your looking for.

Perfect. I've saved the parts link . .. and printed all the elecrical diagrams.

I will attempt to sort out a ground issue . . if all good, then I will try the relay's. However, I sense because there are so many unrelated faults you guys feel it is more likley to be a common issue. If there is no ECU control . . that points to ground. Thanks again for your quick help!!

 

[mfreund]

Sounds like the battery went bad. The last 3 battery failures, I would drive somewhere and have no symptoms. Come back out and the battery would not light the dummy lights. Last time it was at the auto parts store :thumbsup: They tested it and I bought a new one and they loaned me the tools to install.