Hey Guys,

Here's a test for you, hopefully someone can figure it out or help me out...

I rewired my whole dash a while back and put a later model car's fuse panel in to get rid of the issues I was having with the 30 year old corroded one in there, so a heads up some wiring will be different, however...

When I put my brake pedal down, the brakes come on.
When I turn on my headlights, the tail lights come on.
...
When I put my brake pedal down with the headlights on, nothing happens.
The taillights stay the same intensity, no change.

The car is a 1985 Trans AM.

In both scenarios the same filiment on the bulb lights up.

My best guess is the taillight wire on the headlight switch is wired to the wrong place, and when i put the brake on with the headlights on, its working, but the taillights aren't...

Anyone got any ideas, or better yet, a wiring diagram for the headlight switch, brakelight switch, and tailights for 85 transam?

 

This might be of some help.

http://www.austinthirdgen.org/?pid=19

 

Hey,

Thanks, but the link didn't work, in fact the austinthirdgen site isn't working, I'll try again a bit later.
Maybe it's the firewall at work or something.

Did a little more testing yesterday, without my multimeter though, and mainly just following wires, it looks like I may of somehow wired the brake light to the taillights, so when the taillights are on, i'm just sending another 12volt circuit to the same filament, hence no change.

The quick fix is to run another wire from the brake light filament to the switch and then it'll work, but I'd love to know what happened to the original brake light wire....

Also my brake switch has a second plug connector on it, but it's missing, anyone know what it would be for?

---------
| .........|
|.. [ [.. |
|........ |
-------
[ [

where "[" is a spade connector
so 2 at the bottom for the brake light, one with 12 volt and the other the carrier wire,
and then two facing towards the seats with nothing plugged on.

My first guess was something to do with cruise control to turn it off if the brake is applied, sound about right?

 

Yep

 

Ok... So new information, or maybe just a lack thereof...

I did a continuity test yesterday between the contacts on all for sets of brake/taillights and the brake light switch....

All of them came back as a closed circuit, without headlights or brake on.

Am I missing something here? I took all 4 bulbs out and repeated the test thinking maybe one had shorted the others, but still the same result.
How do both contacts have continuity with the 12 volt feed but don't both light up, and how does the ground have continuity with the switch when the bulbs are not in there to complete the circuit?

I checked the wires on the brake lights, the inner set has brown yellow and black, the outer set has brown, blue, and black.

Still can't figure out which is the brake and which is the taillights, but have a suspicious feeling it's brown for taillights and brown/blue for [brake] lights.

Really wish my workshop manual for the car wasn't still in one of my exes boxes of **** she took with her.

Any ideas or info?

 

 

Solved:

Apparently the car never had them wired up properly to begin with.
I traced the headlight wires right back to the connector under the dash with no wire on the other side.
The brake light switch was just wired to a spliced wire with the headlight switch.

I reran a wire from the (light blue wire) connector to the brake switch and it all works now.