Hello everyone I have been chasing this issue down for weeks now and cannot figure it out at all. I've unplugged every light and the fuse blows. Disconnected the harness in the rear and the fuse blows. Disconnected the tail light harness altogether and the fuse still blows. The new headlight switch and the fuse blow yet again. I am down to the point now of checking every single wire about the tail lamp from the fuse box to the switch to see if there is a short, broken wire or something that is causing it. Does anyone have any other idea I can look into?
I had a ‘64 Skylark convertible in college. I could go months with no trouble, then blow the fuse five times in a weekend. It blew one night as I was loading passengers. Turns out I had a wire naked under the rear seat, only touching and shorting when something or someone pushed the seat down. Patrick
I went through this with my 69 GS400. It was a pain in the a**, but I found and fixed it. There are a lot of things that were on that circuit. Here is a thread on it, hope this helps: https://www.v8buick.com/index.php?threads/1969-gs400-blowing-turn-signal-fuse.358879/
To save money on fuses, if you have a multi-meter with "continuity check" (beeps when you have continuity between the leads), you can use it. Just disconnect the battery, remove the fuse carcass, connect one lead to one side of the fuse connector and the other to ground (use the side of the fuse that goes to the lights). If you have a short, the meter will beep. Disconnect things systematically, until the beeping stops. The issue will be within whatever circuit or component you disconnected that caused the beeping to stop.
Did the continuity test and no beep wanted to verify my meter was working right i put the probes in the switch harness and touched it to the side of the fuse that goes to the light as you said and had continuity from that wire to the fuse box. Still stumped on this thing.
Maybe I'm reading your description wrong, but I'm thinking that if it is the power wire to the door switch, you should have continuity to the side of the fuse. Try that side of the fuse connector to a good ground (with the battery disconnected). If you have continuity from the fuse to ground, you have a short somewhere still.
So i got the fuse to not blow and the tails came on. I started the car and they went out again but the fuse didnt blow.
Take your meter and see if you have 12V across the fuse. If so, then go to the tail light wire from the head light switch and see if you have the same there (between it and ground). If so, then work your way back to the lights. Check any of the grounds along the way too.
I am assuming that there was nothing added on the circuit in question? Does the fuse blow with the head light switch disconnected from the dash harness? If yes, then you need to look at the main dash harness. You can use an ohm meter on the non-power tab in the fuse box, put a on lead on the tab and the other to ground. If you have continuity, you have short to ground. You need find out what is on that circuit from the factory and trace all wires on that circuit. You will need a schematic for the model in question, until then this is a guessing game. Go through the wired circuit one buy one. There is a direct short to ground, fry wire, bare wire, screw chafed through, wires malted together. One wire at a time. This will take some time. Good Luck!
For me it appears that the issue is the signal harness. Run your continuity check at the long connector. The replacement runs $85 from OPGI, looks to be a decent part. Jim '69 GS California
