[RF]

I've been trying to figure out this problem for a while. As soon as I put a fuse (20 amp) in for the tail lights it blows immediately. I have no tail lights, brake lights, or dash lights. The turn signals work both ways as well as the back up lamps. Also, the battery light remains on constantly even with everything turned off. Any help would be much appreciated!

["QUICK-SILVER"]

Tell us what you're working on and we'll try to help figure this out.

Any additional info about modifications or what was going on when this started will help. Like charging system upgrades, guage swap, stereo, after market accessories, etc., most anything that may have had wires involved. Even if it was just moving or working around wires to do something else.

[RF]

The car is a 67 Lemans and the electrical system is completely stock down to the radio. Everything worked prior to taking the gauge cluster out for paint. I've ran 3 fresh grounds from the metal on the back of the cluster to a bolt on the firewall, bolted down the cluster with the back brace and checked from loose wires that might be touching metal. When testing the tail light fuse I don't seem to be getting any power on the left side of the terminal, which hopefully helps narrow down the culprit?

["QUICK-SILVER"]

It's looking like somthings wrong with one of the 2 ALT/GEN light wires. Neither goes straight to ground.
Un-plug the voltage regulator and see if the ALT/GEN light goes out. If light does go out, fuse should still blow.

Best I can tell, one wire goes to the regulator and the other goes to the tail/brake fuse.
Looks like the wire between fuse box and light is shorted for some reason. Maybe something wrong where it plugs in the back of the cluster. The ALT/GEN light has an insulated two wire socket that doesn't ground to the back of the instrument cluster.
Look for a short to ground and we'll talk about how an ALT/GEN light WORKS later.

Post back and let us know what you find.

[RF]

Unplugging the voltage regulator turned off the ALT/GEN light and exactly as you said the fuse still blows immediately. In checking the ALT/GEN socket and wiring it appears as though everything is ok, I pulled it out of the dash and made sure nothing was touching and the fuse still blows. Thanks for the help so far, I've been searching through old posts on here and at team Chevelle for any clues to what this might be, but so far nothing is turning up.

[RF]

I made a mistake in one of the above posts so to clarify, I do have power to the left side of the tail light fuse at all times, it was corroded when I tested it before. Also, the GEN/ALT light is only on when the key is off or turned to the left. When I turn the key one click to the right the GEN/ALT light turns off. I'm not sure what happens when the car is started (I can't start it right now)

[kate`s67gto]

Start by disconnecting the body harness to dash harness replace fuse.
if it still blows disconnect the forward lamp harness at junction block. If the fuse blows then disconnect the engine harness. If it blows again then you know your problem is in the dash harness or at the fuse block itself.

[Old Goat 67]

According to the schematic, that lead comes off the fuse to the light switch, through the switch when pulled, to a brown lead that goes to the ribbon cable (white tracer lead), out the ribbon cable in the trunk to a brown lead, then to all the tail light bulbs (low filament).

Look for ground with a VOM, should show low resistance to ground. Disconnect ribbon cable first (by fuse block), clear=trouble out back. Still grounded, trouble in light switch or wiring from fuse block to switch or switch to ribbon cable.
Disconnect plug on light switch. Clear = bad light switch or wire to ribbon cable.
You need to isolate it OR have a pocket full of fuses.
Charles

[LPete]

I diagnose this kind of problem by hooking a lamp across the fuse terminals (I use a headlight with wires soldered on the terminals, but any lamp will work -- ideally you want one that draws significant current). When the short to ground is happening, the lamp will burn brightly. When the short goes away, the bulb goes dim.

This keeps you from wasting fuses, and you can also see the lamp go dim from outside the car as you disconnect things and eliminate the short.

I wonder if there's any chance you accidentally grounded the lighting circuit on the cluster when you ran extra grounds.

[RF]

I will try these out tomorrow and see what happens, with your help I think I will have this narrowed down and found before too long. I really appreciate everyone's help on this. I'd be completely lost without it!