I had a similar problem which was caused by poor mating of wires that caused unnecessary resistance and heating.  I redid the mating using a hydraulic wire crimping tool to make sure that the connection was top notch and that solved the problem.

On Sep 30, 2020, at 9:47 AM, Dan N <dn92610@GMAIL.COM<mailto:dn92610@GMAIL.COM>> wrote:

hi all,

Could ground (-) wires melt/burn under heavy load?

I never heard about it or have seen one till now. I've seen hot/positive
(+) melted wire but not ground (-) one.
My daughter drove her 1998 Carat (stock) with high beams ON and suddenly
smoke came out under the dash, engine died, she pulled over, shut the
engine, waited a bit and restarted the van and the same thing happened
again, got it towed to me.
The van has Jay Brown's headlight relay kit but uses 55/80W bulbs 6 years
ago and working fine till now. The fuses 20,21(low beam) are OK, the casing
of the fuses 9,10(high beam) were melted but the fuses are not blown. In
the back of the fuses panel there is a gray #53 relay and the ground (-)
wire that goes to the ground tree was melted and touched the positive (+)
wire on the same relay.
I replaced the 4 fuses (20,21,9,10) with 15A fuses instead of 20A, repaired
the positive (+) wire, replaced the ground (-) wire with 14 gauge instead
of 16 gauge and installed an inline 10A fuse on it. I ordered a new #53
relay (not here yet) just in case. All working well now.

Sorry for the long description but I try to find out why this could
happen... quite scary and I wonder how to prevent this.

Thank you for any ideas.

dan

________________________________________
Prof. Douglas Toomey
1272 Earth Sciences
University of Oregon
Eugene, OR 97403-1272

https://blogs.uoregon.edu/dougtoomey/
http://geophysics.uoregon.edu
(541) 346 5576 (work)
(541) 632 2526 (mobile)
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