So 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 !
OT ? truck electrical problem
Sep 24, 2019
10 Replies
... 1986 ! ? . . . could be a problem with the 8-track .. :-)
Any signs of mice ?
Any " un-related " non-electrical work done on the truck that might have disturbed fragile 1986 wiring ? eg : tilt-steering adjustments by a new driver ? John T.
What else is on that fuse? Does it still blow if a radio isn't connected?
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'radio' isn't jumping out at me but your eyes might be better.
Sounds like an intermittent short in the supply wire. Try driving with the radio off and see if the fuse still blows. If so, you can try to follow the wire back to find it, or else maybe run a new wire with online fuse from somewhere. You can sell the radio on eBay.
No other work has been done that would have caused this . No sign of mice or any other damage to the wiring . Much as I hate to , it might come down to opening up the harness to trace this out . Gotta give it some more thought before I go there .
Thanks for the link , it should help . I'll have to print some of those out and see if I can tape them together ... it's not clear on those diagrams , but as far as I can tell the radio is the only thing on that circuit . At least it's the only thing that dies .
Can you just run a wire from another place through a fuse to the radio ? That would tell if it is the radio or the wiring. I am sure you checked, but is the fuse the correct value and not just one that someone in the past has changed for the wrong value.
I have considered feeding it from another switched power lead . The 15 amp fuse that was blown when I got the truck back was replaced with the same value - my last one , so when it blew I used a 20 which also blew . I'm pretty sure the smaller fuse in the new Pioneer unit would blow before the supply fuse if the problem was with the radio . And since it did the same with the previous radio , I'm sure the problem is in the truck wiring .
Just out of curiosity, I would put an amp meter across the fuse terminals with the radio off and the fuse removed to see if there is a draw of current for the circuit. I had an instance were there was a drain on my battery with everything off, and it was a power relay for the horn circuit. Not enough to blow the horn, but enough to discharge the battery over time.
Try checking the cig lighter circuit - on a lot of Chevy trucks the radio and lighter share the same fuse
Not on this one , the lighter is always hot . That's where I pulled the memory power for the radio from . A Chevy truck forum post I found indicates that on this model the radio is the only thing on that fuse . On Friday I'll be pulling the fuse block to check for damaged wires behind it - if I don't find any problems there I'll probably be running a new power lead from the fuse block to the radio .
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