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Veteran Advisor
Posts: 5,977
Registered: ‎10-25-2010

on electrical gremlins

I do all the maintanence, and most of the repairs for myself, and my brothers, so I try to keep up on how to fix things.  One new trend that I really don't like, is that a lot of newer stuff, doesn't switch the power 'off'.  The lead is always 'hot', and to turn things off & on, they switch the ground connections.  For example, I had a neighbor who's late-model combine had the taillights come on in the shed for no reason.  He asked me if I had a theory why.  I told him that on a lot of new stuff, the hot wire is always hot, and the ground wire is now the 'switched' wire.  Turns out he had a mouse in the wiring, and gnawed through the ground wire, and it was touching a bolt or something, completing the circuit.  Could your problems possibly be a ground wire with thin insulation someplace, making contact?

The other thing I am seeing, that I REALLY don't like, is a common 'hot' wire that runs several things, and then separate grounds for individual components, or, worse yet, a computer chip, at the end of a wire, in a little junction, that controls which circuit gets completed via a 'signal' sent down the wire.  I am hearing of a lot of little gremlins in JD combines that are now 2-4 years old or so, having lights turn off & on when you call for the grain cart over the radio, and even one case of the combine just dying once or twice a day, and restarting after you turn the main switch off, and on again (turns out 'shielding' a section of wiring harness cured the problem, took a JD tech half a day to figure it out).

What worries me about this trend, is what happens when the wiring gets older, and those always 'hot' wires get a crack in the insulation, and get into a situation where it can 'spark' every once in a while, but not short out solidly enough to blow the fuse?

 

Anyhow, the point of my long story, is that in about 2/3 to 3/4 of the odd electrical gremlins in new machinery I have seen, tend to involve circuits where the component is turned off and on by switching the 'ground' side, rather than the 'hot' side.  I was curious if your tractor had the same sort of setup?