As a new owner of a 1969 (L71) Corvette, I was hoping someone could help me an electrical problem. The tail lights on the car light up as soon as the battery is connected and the back up lights come on as soon as the key is turned to the "run" position (no matter what gear the car is in). I've disconnected the brake light switch (at the pedal) and the tail lights still stay on. I don't see any obvious problems with the tail light/backup light wiring. Is there a common problem with these lights or should I be looking at two different issues? Thanks in advance for any help.

 

The tail,brake,backup,side marker lights, and interior cabin light at the back of the storage compartment, all have a common harness. The only wire that should be connected to the battery (through a fuse) is the interior cabin light. It will come on when you open the door.

The above harness terminates in a multiwire connector half which mates to another connector half right under the fuse block. You probably should look at this connector to see if someone has spliced wires together. To get to this connector you need to pull the carpet away. The fuse block is located above where your left foot would normally rest.

Also look underneath car at the back for any obvious indications of the harness wires being cross connected by Bubba. About 1/2 of the harness is underneath the storage compartment carpet and so is hard to see if there's been any crosswiring. You'd have to pull the carpet and door sill plates off to look at the carpet.

What I'd do after making a visual inspection of the rear exposed harness at the tail of the car.....

Access the above connector. For easy access remove the drivers seat and peal back the carpet exposing the connector and fuse block.
Once again look for Bubba's tampering. Next pull the connector apart, and begin to probe the connector half connected to the inner firewall main harness/fuse block. With a color coded wiring harness diagram from Dr Rebuild, take a voltmeter and look for voltages with the ignition key and headlight switch off. Only the connector terminal providing 12 to the cabin light should have voltage. The others should read 0 volts. (The cabin light should have 12 volts, because you're doing this test sequence with the door open.) If the connector pin for the brake lights has 12 volts, then Bubba has probably done something to the main interior fire wall harness. Next put the ignition key on, with the headlight switch off, and you still should only have 12 volts to the cabin light. Are any other connectors energized? If so they shouldn't be. Press the brake petal, the connector pin that supplies 12 volts to the brake lights should show 12 volts.

Let's hope the problem is just that Bubba has screwed up your rear harness. Maybe you can repair the harness once you find the problems. You can buy an entire rear harness for about $250 (with fiber optics), but you have to lift a lot of the rear carpet to replace it. Also, the door open switchs are part of this harness, so more carpet lifting to replace this part of the harness.

Let's hope the problem is not in the interior firewall harness...That's a much longer story.

 

Thanks for the detailed information. The only new wire that I see attached to the fuse block is one for an electric fuel pump (located near the fuel tank). I'll disconnect it to see if that has an effect but I can't see how it would. By the way, why would a PO install a second fuel pump? The mechanical one was replaced when the engine was rebuilt not long ago and seems to be working fine. Thanks again.

 

I agree with the first response. That rear wiring harness has everything going to the back of the car. Tail, brake, fuel gauge, backup, side, rear interior. If the connector is disconnected and you still have any of these lights coming on, then Babba has been there. The cable is easy to find under the carpet by the driver's door, just pull up the door sill plate and pull back the carpet. It'll lead up to the connector just under the fuse block. There shouldn't be any other wiring going to the back of the car.

Andy

 

Well either the mechanical one failed and left him stranded and- he wanted a backup-or he was using nitrous.