No Brake Lights on '86 Carrera

[NoSub]

I have no brake lights when stepping on the brake pedal. Fuse looks good. Searched and found many posts about the MC Brake Light Switch. Checked them both with Ohm meter, and they appear to be functioning correctly. Unplugged connectors and tried jumping them with a wire directly, and that doesn't light the lights either. Replaced both bulbs for the heck of it, but nothing still. Also, my Cruise Control stopped working about a month ago. Not sure if that's related as I only learned about the brake lights not functioning last week. They could have been out for a month though. Does anyone have any suggestions as to where to go from here?

[spuggy]

Originally Posted by NoSub

I have no brake lights when stepping on the brake pedal. Fuse looks good. Searched and found many posts about the MC Brake Light Switch. Checked them both with Ohm meter, and they appear to be functioning correctly. Unplugged connectors and tried jumping them with a wire directly, and that doesn't light the lights either. Replaced both bulbs for the heck of it, but nothing still.

Which connectors did you jumper?

One of my rear clusters recently stopped working. I discovered the bulkhead connector in the corner of the engine bay wasn't very snug.

That made no difference. Got under the car and found a ground connection for the cluster on that side that obviously hadn't been re-made when the motor/trans was re-installed. About a year ago. And I know the lights in that cluster were working much more recently than that...

Bolted the ground connection up and the lights worked great. Moral: electricity will find a path to ground if it can - but it might not be the path you think it's taking...

Originally Posted by NoSub

Also, my Cruise Control stopped working about a month ago. Not sure if that's related as I only learned about the brake lights not functioning last week. They could have been out for a month though.

Cruise control uses through the stop light filaments as ground, IIRC. No stop lights = no cruise.

Check the obvious stuff; don't overthink it. Do you get 12V to the bulb holder? Does the bulb holder have a good ground?

[NoSub]

I unplugged the connectors to the MC, and then inserted a wire into each of the connectors (1 wire into each connector). I do get tail lights when I turn on the lights, so I believe that means a good ground to the socket. Being that both tail lights and the third brake light do not illuminate, I'm guessing it's "somewhere up the chain", and not the sockets themselves. Any suggestions on which grounds to check? Is there another point where all three wires would connect to? Sorry if these questions seem elementary, but I am pretty weak when it comes to electrical experience.

[kidrock]

I'm an electrical idiot, but I think it sounds like your brake light switch.

[NoSub]

But if I by-pass the switch by jumping the connectors, why wouldn't the lights illuminate?

[gregwils]

Here is the Bentley diagram for the light circuits. I don't have time to look more closely right now, but perhaps this will help you or someone else to venture a guess. You may want to check fuse #4, it appears to control both the brake lights and the cruise. If you install the fuse (8 amp) and it blows again, you will need to determine the cause - bad grounds, hot wire grounding to chassis, etc.

[al lkosmal]

Check your fuses again. My tailights went out and the fuse was good. however, when I checked the switches, I traced the wire from the switch (green with a blue stripe in your photo) back to the fuse block and it was connected to the fuse location next to the one labeled for the stop lights. I replaced the fuse in that location and all is well.

PS: this did follow an electrical incident that blew a fuse or two.

[dshepp806]

Check the fusebox connections carefully,..retighten connections. I'm assuming your wiring in the car is factory/normal.

Have you voltage (measured/refrenced to ground) on both sides of Fuse4?

Doyle

[NoSub]

After determining there was no power at the MC connectors, I traced the wires back to the fusebox. Per dshepp806's suggestion, I checked the connection to the fusebox and found the wire to Fuse4 did not have a solid connection. I pushed it up and tightened the screw -- bingo -- I now have brake lights! Sometimes it's the simple things... Thanks everyone for your suggestions.