Join Date: Jul 2003
Location: Rancho Santa Margarita, CA
Re: Fuse problems
I had this same issue after replacing all my wire harnesses a couple years back.
I had installed new harnesses from M&H. Then the problem showed up. I disonnected the rear harness from the connector up near the fuse block and still had the problem. Then I disconnected the front light harness from the bulkhead connector in the engine compartment, and the fuse stopped blowing. I pulled that new harness out and took it over to M&H. They tested it and it was good, and being the swell guys they are they gave me a replacement harness anyway. When I installed it, the problem was gone. M&H suspected I had a short in one of the sockets that they for some reason could not detect. The only noticeable issue with the harness that was blowing my fuses, is they had not greased it with that gooey black goopy stuff and I installed it any way. Replacement harness was gooped.
Follow the advice already posted on the brake lamps etc. But also check your parking and marker lamps. The side marker lamps can sometimes short in the socket if the leads are not straight.
Narrow it down to the front or rear harness by disconnecting them one at a time and then turning the lamps on to see which harness makes the fuse blow.
Buy a couple boxes of 20A fuses and then go one socket at a time. Remove the bulb, turn on the lamps and see if the fuse blows. Sooner or later you'll find the right socket, then you can narrow it down to the socket, the bulb or the wiring to that socket.
If you have to, pull the suspect harness out and inspect the entire length for damage. It's not as hard as it sounds.
Also check all your grounds to be sure they are clean.
Also inspect the headlamp switch wiring in your main harness uneder the dash. Headlamp switches get corroded over time and are pretty cheap, so if nothing else works out, replace the switch.
ZZ502; TKO-600; 3:73 Moser 12-bolt w/Detroit TruTrak; SSBC Force 10 4 wheel power disks;QA1 Coil Overs; Global West Tubulars;GNX Quick Ratio 12:1 PS; Hotchkis Front Sway Bar
87 Buick Grand National (does 10's)