I just remedied this same symptom in 87 truck. This is referred to as ignition circuit. It splits just above fuse panel. Red wire drk blue tics. I opened circuit at split & reconnected to source. No problem on wire running forward to engine (choke & who knows what else), but blew fuse when connected to leg going up behind, along dash, then under passenger seat, beneath cab, over tranny to back-up light switch. This is where I found short. Rewired a 4' run from reverse light sw to "clean" wire just below cab outlet. (Under passenger seat). I also rewired a new fuse holder in line just above fuse panel, rehoined the two wires @ split & have been driving along happily ever since. This circuit does go on to rear for turn indicators too, so you might check tail lamp assmbly's too. I feel fortunate it wasn't something up front. This circuit wanders all over the vehicle, but the red wire w/drk blu tick showed up again @ reverse light sw. I didn't see it up front and once I did rewire @ tranny sw problem solved. It didn't come easily though & I hope this helps you. DO NOT use higher amp fuses in hopes of quick fix. The resultant damage could be extensive.
Sunday, April 22nd, 2012 AT 8:55 PM