87 gw engine harness gets hot when ignition is on.

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Cheapthrills
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87 gw engine harness gets hot when ignition is on.

Post by Cheapthrills »

What would be the cause of an engine wiring harness getting hot with no obvious shorts under the hood? Ignition switch?

briman2021
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Re: 87 gw engine harness gets hot when ignition is on.

Post by briman2021 »

Not Wagoneer specific, but its likely that resistance is what is causing your heat (I'm assuming you aren't trying to pull extra amperage) I have seen this in bad/loose connections, corrosion etc. Check grounds/connections for corrosion, of if they are loose, start where the harness is warmest. If they all look good, it could be a pinched wire where some of your braided wires are cut inside the insulation.

One of my friends is a very talented mechanic and his words of wisdom to me on electrical problems are that 90% of problems are at the ends of the wires, rarely in the middle.

Most notably, I had a nut on a ground clamp come a bit loose on my mig welder, and as I was welding, the point where the nut was actually got red hot. The welder functioned normally the entire time.
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tgreese
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Re: 87 gw engine harness gets hot when ignition is on.

Post by tgreese »

There is a resistance wire between the bulkhead fitting and coil. It could get warm, and that would be normal. There is also a resistance wire between the ignition switch and the alternator, which also could get warm.

You can take the wires out of the loom and feel them individually. The plastic loom is meant to be opened and put back. Once you know which wire it is, you can trace it back to the source either by hand or by following it on the wiring diagram.

As above, the wires very seldom fail in their middles. Connectors are a common source of electrical problems.
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Topic author
Cheapthrills
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Re: 87 gw engine harness gets hot when ignition is on.

Post by Cheapthrills »

So it's a larg red/grn wire that splits off to 2 yellow and one black wire. I suspect it is coil but unconfirmed as of right now. Still sorting out mods made by po that removed fusable links and installed fuse block 30 amp fuses
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babywag
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Re: 87 gw engine harness gets hot when ignition is on.

Post by babywag »

Cheapthrills wrote:So it's a larg red/grn wire that splits off to 2 yellow and one black wire. I suspect it is coil but unconfirmed as of right now. Still sorting out mods made by po that removed fusable links and installed fuse block 30 amp fuses
That's resistance wire for coil/alternator.
I've never checked one(for temp.), but guessing may be normal?
-Tony
'88 GW (aka Babywag)

Topic author
Cheapthrills
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Re: 87 gw engine harness gets hot when ignition is on.

Post by Cheapthrills »

Didn't work on the 87 today , took the 90 out wheeling instead :fsj:
For my bday present

Posted small report in trails and tails, it' the hackett gulch thread

Topic author
Cheapthrills
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Location: Sedalia colorado

Re: 87 gw engine harness gets hot when ignition is on.

Post by Cheapthrills »

Well i figured it out.... typical ignition control module... but it got a new to me distributor too...

Now to figure out the nasty tick it has.

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