Ok, so my car's electrical is now officially p*ssing me off.

I had noticed for a while that the park lights were coming on when the brakes are applied...annoying but not the end of the world.

But doing some work this evening on the car noticed the issues are more than that.

When the lights are off everything work ok for the most part other than the park lights coming on with the brakes.

However, when the lights are on the turn signals don't work and neither do the brake lights. The tail lights light up fine when the lights are on but they just burn the same whether the brake is being pushed or not.

Any ideas?

 

Sounds like you have a ground that isn't hooked up. My guess would be the one in the trunk. Sounds like your brake lights are trying to run thru the other lights to ground. You have checked the bulbs.....right?

 

The bulbs are brand new. Actually, I just installed brand new bulbs last night. Upgraded to the LED tail lights because the others were really dim. New LED's are much brighter and work great provided the head lights are not turned on, LOL!

The car has been doing these things since I bought it in April. A month or so ago I replaced the rear wire harness and then not so long after that I replaced the tail light housings, reverse lights, etc. Didn't replace the various things thinking it would solve the problems just some worn out stuff that needed to be replaced due to wear / tear.

Before that my lights had started cutting out and flickering that required changing out the light switch to fix, so that switch is not very old either but didn't do anything to fix the other issues.

Is it possible there is something grounded incorrectly under the hood or under the dash?

Seems like someone a week or two ago had mentioned something about a "ground strap" off the battery. I was studying the wire diagrams last night and can't figure out what exactly I would need.

Currently, I have the negative cable coming off the battery and bolted into the block which appears to be what the wiring diagram shows. The only thing that looks perhaps a little strange is there is a second wire that appears to be a ground wire coming off the alternator that is attached to the block with the same bolt...that seems odd but haven't figure out if it is wrong or not just yet.

 

You also need a ground connection from the battery to the car (body or frame). The one going to the block is for the starter and motor grounding only. The car has to have a separate ground to the Battery.

 

Headlight switch possibly?

 

I would look more for a ground that is connected to the lights. Can't remember off hand exactly where they are but I believe there is one in front of the battery, from the front lights.

I really think your problem is with the brake light ground though. You said other lights work but, act up when brakes applied...

 

Just in case you are not sure, the trunk ground wire connects to the trunk lid latch brace. The piece that stablizes the tail panel to the trunk floor behind the gas tank. At least it's that way in the 69

 

The light switch is pretty new, a month or two old. The old one was getting old and the lights started cutting out on me so had to replace the switch to get the lights working again.

My turn signal harness seems to be getting pretty worn out. I have a new one on the work bench just haven't had a chance to install it yet, any chance that could be a contributor to my problems?

The rear ground in the trunk if memory serves....on each side there is a ground wire that attaches to one of the four bolts that holds in your tail light housings on each side. That appeared to be what the wire diagram had for a '66 but going to check it again just to be safe.

I am thinking maybe having a ground from the battery to the frame might be the problem but not sure what sort of set up I could get to make that happen, does anyone have a picture of something along those lines or an idea where I could buy one?

 

LOL SAME EXACT PROBLEM I HAVE. I know mine is a short within the steering column. I can hear it. Try there. Only thing different is when my lights are on they will flicker from the short. But yeah, my lights are working the same way yours are right now. About to try and check it out tomorrow.

 

Well that was part of the problem....I followed along with the way the car was wired when I got it but when I typed this above it started me thinking....checked the wire diagram again then went out and moved the ground to a bolt other than the one that holds on the tail light housing.

At least now, my turn signals work with the lights on...still haven't figured out the park lights coming on when the brakes are applied but at least I just resolved one of the problems.

I haven't had a chance to see if the brake lights work with the lights on now but when my boys get home in a bit I will have them push the peddle with the lights on so I can stand behind the car and watch. Even at seven they love to help me work on car stuff even if right now they are not good for much other than helping push the brake peddle or things of that nature. I refer to them as my pit crew in training :-)