On Sep 24, 2019, Terry Coombs wrote
(in article ):

When I got my truck back from our son , lots of things that he just
couldn't be bothered to fix . One thing is the radio power supply . He
did tell me that the radio had "died" , turns out the fuse (in the fuse
block) keeps blowing . I've got the dashboard apart enough to check the
wiring harness and supply wires , can't find any cuts or anything that
looks like damaged insulation ... it works just fine sittin' in the
driveway , but within a few miles driving it blows the fuse . I figured
it was the radio/CD player unit so I got a new one , does the same thing
. I'm really puzzled by this , from the way the fuse was spattered it's
got to be a dead short to ground . I think it very unlikely that the new
radio/CD unit is bad - the old one did work when I replaced the fuse ,
for a few miles same as the new unit . This is an '86 GMC pickup , I'm
hoping someone here might be aware of a known problem area that I might
check ... I gotta have tunes !

It´s classic for sure. The power wire is bouncing around as you drive, and
over time the wire insulation was worn through, allowing contact between
copper wire and some part of the steel body.When you find the spot, it will
be pretty obvious visually.

Solution is to find out where this is happening, and mechanically prevent
further contact.

Joe Gwinn