Brake and running lights problems

[patrick66]

On my '66 Imperial convertible, I am having problems with the taillights and brakelights. Here is what I have:

With everything plugged in and hooked up, and the engine and all lighting turned OFF, the RR outer lamp stays illuminated. If I unplug the wire from the brake switch, it goes off.

When the brakes are applied, NO rear lamps illuminate.

When the headlights are turned ON, all of the brake lights come ON, instead.

The RR turn signal lamp works fine. The LR does not. Both fronts DO work.

The tag light does NOT come on.

I do have the FSM, but am not finding it real friendly in troubleshooting. I have replaced ALL SIX of the rear bulbs, cleaned the contacts and grounds, and have used dielectric grease in installing the new lamps. My interior lamps work fine; and since they are on the same circuit, the fuse is good.

Any ideas??? Thanks!

 

[Big_John]

IMHO, I'd look for a bad ground somewhere, most likely in the rear of the car.

The grounds might look good where they fasten to the bumper, but the bumper itself might not be grounded to the body. Try running a jumper wire from the battery or a known good ground to the bumper or tail light ground(s) and see if that helps.

 

[mr. fix it]

check your bulbs! there may be one that is shorted internally..

Have you changed any lately?

 

[68-300]

Check the turn signal switch in the steering column, it's probably worn down, needs cleaning or has to be replaced. All power to the brake lights and rear turn signals run trough it and are switched by it. Also check its wiring that runs down the steering column, it may be damaged somewhere.

I would also check the brake light switch, it should never give power when no brakes are applied, they are cheap and easy to replace.

Tag light is a separate issue, it has it's own wiring that isn't switched with the turn signal switch like the rear lights, often it is combined with the wiring of the side markers.

 

[68-300]

Check the turn signal switch in the steering column, it's probably worn down, needs cleaning or has to be replaced. All power to the brake and rear turn signals run trough it and are switched by it. Also check its wiring that runs down the steering column, it may be damaged somewhere.

I would also check the brake light switch, it should never give power when no brakes are applied, they are cheap and easy to replace.

Tag light is a separate issue, it has it's own wiring that isn't switched with the turn signal switch like the rear lights, often it is combined with the wiring of the side markers.

Small correction on my reply; the tag light is powered from the left rear lights wiring.

It looks like the brake/turn light wiring is used as ground for the rear lights, since the left turn signal isn't working I would recheck the grounds of the taillight housings starting on the left.

 

[patrick66]

I'm going to see what's what today, assuming the temp stays below 90*F. This weekend was miserable in terms of getting car stuff done!

 

[BJS racing]

The housing being mounted to the car is the ground on most all of these cars. I would take one of the nuts off of each housing and make a ground wire for each housing and run them to a chassis ground. This tends to show up alot when someone has repainted a car recently and is putting it back together.

 

[Mr C]

How are the front signals behaving? Do you have a "dim" condition up front too? When I was restoring the 74 D100 pickup, it had the same issues you describe. In my case it was the switch...if I wiggled the knob, the dim signal went out...it was surely a fire waiting to happen. I replaced the switch and every bulb, as well as cleaning/ verifying every ground. Those press in light receptacles are notorious for bad ground, as mentioned...I had to do the ground wire fix too.

 

[patrick66]

The front parking lights/turn signals appear to be working fine, as do the dash turn indicators. I did find yesterday where a critter was dining on some of the wiring insulation near the LR turn lamp. There are two exposed wires, but neither are touching. I'm going to splice a patch at that point and see what happens next. That may well be the whole problem. Hopefully!