Blinkers work only once then blow a fuse

[sonofspain]

Hi all. I've got an 83 C30 which came as a C&C from the factory to the Air Force who put a water tank on it. When I got it the tank was gone and the wires going to the back of the truck were cut off right at the back of the cab. When I bought it I was way out of state so I bought a pair of trailer lights and wired them up and mounted them to the rear of the frame for the drive back home. All the lights worked before I left. After leaving a gas station I noticed the blinkers didn't so I pulled over and first checked the fuse box and sure enough the 10 amp fuse was blown. I replaced it and they worked next I used them and then they didn't after that. I figured the most likely problem was a short but couldn't see how it would be in the wires I ran back as they were brand new and easy to see since there was no bed on it and the brake and running lights worked fine. I still haven't been able to figure out the problem. Any ideas? Mark.

[bd]

You already pretty much summed it up - intermittent short.  Look in the 1983 GM Wiring Manual and start tracing circuits.  The turn signal fuse also protects the backup lights, so make sure you don't have a light green wire in the rear lamp harness touching ground.  Will the T/S fuse blow under controlled circumstances, like sitting still while you attempt to troubleshoot?  Check the turn signal switch pigtail that exits the column under the dash.  It is supposed to route down-column inside a stiff plastic sheath.  If the sheath is displaced or missing, the pigtail could be chaffed or cut.

[sonofspain]

Thanks for the suggestions and the link. I'll check it out and hope I figure it out. Take care.

[hatzie]

Thanks for the suggestions and the link. I'll check it out and hope I figure it out. Take care.

Do the brake lamps work?

Yes?  The backup lamps are the likely culprit...

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