OBS - Neighbor's Truck Question

[BuiltToWork]

My neighbor has an OBS truck he restored (he is a paint and body work guy).
He says that every time he starts the truck with the radio on, it blows a 15amp fuse.
He also says that radio off, truck starts fine and can turn the radio on after startup.

I'm fishing for a quick answer - if this is a common problem.
I am a member of the GMsquarebody forum, but I want to wait to ask until I get a chance to walk over and check it out myself.

My first guess is a grounding problem, I'll download the service manual once I find out what year/type his truck is.

Buddies truck year/make/model - unknown except for that it is a square body. Will update this tread when I get more details.

 

[movietvet]

Recently, on my girl's 1990 K2500, I had a need to set the emergency flashers and after I did that and shut them off, I discovered I had no brake lights. Fuse was blown and continued to do so whenever I turned on the emergency flashers. Come to find out that the fuse I had been matching with the old fuse was the wrong amperage. I looked closer and found the fuse location called for 20 amp instead of 15 amp, that was in that location.

I also had an old square body, years ago, that when shut off the ignition at night, with headlights still on, the engine kept running. If headlights were off and then shut off the ignition, the engine shut off as should. Found rubbed thru ignition and headlight wires insulation at the back of the under dash fuse box. Strange things can happen.

 

[Road Trip]

My neighbor has an OBS truck he restored (he is a paint and body work guy).
He says that every time he starts the truck with the radio on, it blows a 15amp fuse.
He also says that radio off, truck starts fine and can turn the radio on after startup.

I'm fishing for a quick answer - if this is a common problem.
I am a member of the GMsquarebody forum, but I want to wait to ask until I get a chance to walk over and check it out myself.

My first guess is a grounding problem, I'll download the service manual once I find out what year/type his truck is.

Buddies truck year/make/model - unknown except for that it is a square body. Will update this tread when I get more details.

Hello BuiltToWork,

When you get more details, please ask which fuse blows? It would be easy to assume that it's the Radio fuse,
but given scenarios like the one that movietvet shared it doesn't have to be that fuse. Also, does the truck
have a stock radio, or is it aftermarket? Stock wiring? Or custom wiring where the radio/outboard amp(s) are
connected directly to the battery terminals?

One more thing. Did the radio ever work correctly? (No fuse blowing while starting engine with radio on?)
If so, what date did the fuse blowing start? And more importantly, what changes were made to the truck
right around this window in time?

The more info the better. If the truck wiring still matches the FSM this will be straightforward. On the
other hand, unique to this truck wiring mods could be breaking some rules.

With enough data we should be able to figure this out. Sounds like an interesting problem. (!)