Current flows in a circle... from the positive node of the battery, through
the positive wire, to the load, then through the ground wire to the
negative node of the battery. If you use a proper sized wire for the
positive side, but an undersized ground wire, then it can absolutely burn
under load.

Does this make sense?

Thank You,

Ken

On Wed, Sep 30, 2020 at 9:48 AM Dan N <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
>