Soulblood

Hello. I need some help before I go crazy, lol.

I am almost done restoring a 72 Cutlass Supreme. It's road ready, but I will not be able to pass a PA inspection as the lights are not all working. To start the right hand rear tail light, brake light, and turn signal all works wonderfully. On the left side is a different story, the tail lights work, but no brake nor turn signal in the rear. Front turn signals work great. The lower socket in the left rear was loose from the housing with wires loose as well, I replaced the entire socket, however, the problem still exists. When I test the lines with lights on, I have a reading of constant voltage for the brown tail light wires, and the yellow brake/turn wires, without brake pedal being depressed. The right side only has voltage to the green brake/turn wires when brake pedal is depressed. Any idea why there is constant voltage in the left rear side? Additionally, the second filament is not lit even with the constant voltage. Not sure if that is typical or not? Thank you!!

Lady72nRob71

I bet that once the load of a bulb is added, the voltage on the STOP/TURN goes to 0. It is possible that there is an issue in the turn signal / hazard switch. Try to exercise the hazard switch to see if that helps. If wiring all looks good with no pinching or hacking, then we will need to dig deeper.

Soulblood

Last night I had the bulbs in and the wires exposed to test. The bulbs came on, only 1 filament lit up in the bulbs, and it still was showing voltage through both sets brown & yellow. I forgot to check to see if the hazards work, and the hazard switch. I will check that tonight. I figured the turn signal switch was good as all the other turn signals work, but maybe I am being too naive? Thanks for replying so fast!

Highwayman

Check for a good ground. If you have a poor ground one filament will attempt to find ground through the other filament and show up as voltage on both. Remember that voltage does not light a bulb, current does and that requires a complete circuit.


When you check the 4 ways do it both with and without the running lights on. A bad ground will make the lights do all sorts of squirrely things. Like making the tail light blink for example.

Soulblood

Ooooh ok. That makes sense. Do you think this would coincide with the Fuel tank sending unit? The fuel gauge was working when I did not have the bumper nor lights installed. Now it is pegged way past full and does not budge, which I have read on other posts is what happens with open circuit.

Highwayman

It coincides in the sense that stuff happened after you took the car apart and put it back together. It could be related or it could be two separate problems. Don't get caught up looking for a common problem. Shoot one problem at a time and if it is a common problem it will show up when you find something.


So the gas gauge worked until you hung the bumper? I'm not getting any ideas on that one. It's only been about 20 years since I dropped a tank. Does the tank have a ground wire to the body/frame or does it rely on metal to metal contact? If it doesn't have a ground wire, did you do a nice job painting everything up real pretty?

Soulblood

Haha, you know it! Its all nice n purtty. Which thank you for pointing out, cuz that could be my issue, I even painted up the bumper brackets. Good Advice, lights first, then I will worry about the gauge if it is still messed up. Then on to headlights, that I am hoping is just burnt out bulbs and nothing to do with wiring. Fingers crossed, lol.

Soulblood

Haven't had a chance to work on it for a few days til tonight. Tried the hazard lights and they all work flashing, except the same left rear side. So ran a ground wire, did not work, then did the worst and bumped one of the live wires. It sparked and now no rear lights at all. LOL. Voltage is at the fuse, and the fuse did not blow. The headlights and front parking lights come on still, just no rear lights. I'm assuming I blew a switch somewhere?

Lady72nRob71

No stop, turn, or tails? Parking lights still work? do the flashers in front work (but prolly stay on rather than flash?)

Soulblood

Nothing in the rear now, no lights at all. Yes, front stay on, dont flash. Since there is volts running through the fuse, it must be the light switch. I will have to get into the dash this weekend and test the wires & switches. Hopefully I can find enough time! Thanks for all the replies. If I am able to resolve it, I will post it! Fingers crossed, lol.

Lady72nRob71

Check the rear body connector in the trunk, too. If the brake lights do not work, then the light switch is not the issue, as those filaments are on a different circuit.
So the side markers or lic plate light are dead, too?

Rickman48

In putting together many cars others have taken apart, I've found the ground wire in the tailight loom, which could be anywhere from the back seat to the rear body panel, is usually the problem!
Trace the wires from under the dash, under the carpet, under the back seat, for crushed or cut areas, and from the back seat to the rear body panel for the ground wire!
I've used those 'gripper' flat washers [pronged] instead of scraping or sanding fresh paint, without a problem, also.
Should be a hole close to the wire for a sheet metal screw, too.