81 911SC Brake light fails with lights on

[mstinson15]

Good afternoon from Germany,

I recently purchased a 1981 911SC while stationed here in Germany. I failed to notice the lightiing issue when I bought it and will fail inspection if I can't get it resolved.

When I apply the brakes, the drivers side is very dim compared to the passenger side.
When I turn on the driving lights, the drivers side brake light stops working all together.
With the lights on, the passenger side brake light is also less bright than with the lights off, and then when you apply the brakes the passenger side gets very bright.

Turn signals work fine

Reverse lights do not work at all either.

Brake warning light is on. It resets fine, but then works fine until you turn the lights on then it illuminates again.

Here is youtube video link for reference that I took showing this.

https://youtube.com/shorts/U8Za0nKMZlc?si=cf1EymddWAy9tlkN

https://youtube.com/shorts/U8Za0nKMZlc?si=cf1EymddWAy9tlkN

I truly appreciate the help. BTW I did check the bulbs and they are working just fine. Brake and Reverse lights bulbs are good.

I found another thread with similar issue and his turned out to be the prongs on the bulb housing, and another was something to do with the engine compartment light, but so far no luck.

[EC900]

I’ve seen this sort of problem on domestic cars. Im not electrically savvy but error prone as the next novice in that department. I once swapped a 1157 for dead 1156 on a motorcycle trip to be compliant legal in an not-so-friendly out of state road trip, forgot about swapping back when I noticed the mishap in functionality.

Are they all the proper bulbs… #1034 originals spec or the universal dual filament 1157 ? Not that 1157 won’t work, it might be an 1156 single filament used as a quick replacement at some point.
The bulb (posts) can only be inserted one way, wrong bulb/wrong socket, maybe the the previous owner put the left bulb in wrong orientation and not making proper contact drawing voltage/watts and imbalance to other filament or right side circuit So look closely at the socket itself for damage.
Check and clean wiring, contacts and for grounding faults too.

I can’t say if the Brake dash warning light will detect brake wiring faults but it is wired to the brake circuitry, (including the handbrake, that switch itself is difficult to set and get the dash light to shut off, I unplugged mine) check the wiring on the master cylinder brake light switches terminal connections.

[Dpmulvan]

Pull the driver side housing probably corrosion back there.

[Mr. Merk]

Originally Posted by EC900

Are they all the proper bulbs… #1034 originals spec or the universal dual filament 1157 ? Not that 1157 won’t work, it might be an 1156 single filament used as a quick replacement at some point.

This, I had this happen recently!

[PeteKz]

I just replied on your other thread. Please only start one thread.

[mstinson15]

Originally Posted by PeteKz

I just replied on your other thread. Please only start one thread.

Yeah that was purely by mistake. If a mod could take it down that would be great. I was making it from a government computer and it got frozen on the submit so I thought it did not go through.

[mstinson15]

So, after good advice I traced it to several issues.

1) Drivers side housing was corroded. I pulled housing apart and cleaned up every connection.
2) The drivers side ground was covered in gunk. I pulled the ground off, cut the wires, rewired the three ground wires, and cleaned the ground itself. This got the brake lights working properly.
3) The reverse switch has been tampered with before. There two connectors have been clearly reinstalled before but pretty poorly. I pulled the wires off, ran extra length on them, and put them together and the brake lights are good. Have not pulled the switch out yet but it's a bit of a mess where the wires come through the tunnel. I'm going to re-organize all of that mess.

[PeteKz]

Originally Posted by mstinson15

Yeah that was purely by mistake. If a mod could take it down that would be great. I was making it from a government computer and it got frozen on the submit so I thought it did not go through.

No problem. It happens.