Brake Light Not Working: Troubleshooting Guide

Hello everyone,

I noticed the following strange phenomenon today:

'When braking, the front left parking light sometimes turns on. I haven't been able to check the rear lights yet (it's hard to see because the brake light is brighter). For some time now, the GRA (presumably a system related to parking assistance) has intermittently stopped working, but only when the lights are turned on. Additionally, I've been getting error code 741 (implausible brake pedal signal) occasionally for a while. According to the error description from Michael II, one of the two pedal switches is likely defective. This would also explain the erratic behavior of the GRA, as it would then receive a signal indicating the brake pedal is being pressed. However, the fact that it seems to depend on the headlights suggests a ground problem. It doesn't seem to be the typical issue with a missing ground connection at the taillight, because the turn signals and reverse light remain dark.'

Before I start troubleshooting, I would appreciate any tips or experiences you might have.

Regards,
Martha.

Sorry, I forgot: It's a 1997 A4 AFN.

either it's the classic mass error.

or a multiple cable break affecting the brake/tail light connection.

Try connecting the taillight to the ground using a crocodile clip first.

Are there any DIY projects related to the electrical panel that I should be aware of?
'I once had a case where the vehicle owner had installed some wiring to connect his DIY projects. He had stripped the insulation inside the vehicle and connected individual strands of the wire to the fuse box. It's amusing because the fuses don't immediately blow when using low-power devices...'

CU Gremlin.

Hello Gremlin,

I can't completely rule out issues related to the fuse box. I've actually installed an auxiliary battery system (ABS). I only just noticed the problem with the parking light in the underground garage, so I don't know how long it's been happening. However, the ABS is my favorite gadget and worked perfectly for months, until about two weeks ago when I started experiencing occasional problems with the ABS and intermittent error code 741. That reminds me, I've also been hearing the warning chime occasionally for about two weeks now, when I remove the ignition key, open the door, and still have my foot on the brake. That's probably a sign that the problem with the parking light has been going on for a while.

And I don't want to hear anything about multiple fractures or polytrauma...

Best regards,

Regarding Cable PolyTrauma.

I just discovered something on my G3 VARIANT that manifests itself as a peculiar trunk light issue, but it could also be causing your problem.

I have license plate lights and a third brake light installed in the tailgate. All the cables are broken at the rubber grommet between the tailgate and the body.

If they're having a party there, basically causing a short circuit, you'll experience a chaotic display of brake lights and turn signals, and you'll likely be overwhelmed by the flashing rear lights.

If your A4 is a sedan, you probably don't have a brake line running to the tailgate, do you???

m;

Hello Dieselmartin,

It's an Audi A3 (Avant). So, the tip might be a good one. Thanks!

@dieselmartinn
I know that all too well.
Is this a common problem with the Audi 80?

Yes, that's a common problem with the Audi B4.

However, this will also be the case for the B5, because the cable routing and the rear hatch hinges are, at least for the sedan, identical in their mechanism.

Similarly, the standard procedure applies to the G3 variant.
I've had that happen twice already.

Also, the same applies to the Audi 100 Avant C4.

I've found a good solution for myself .
Conrad sells a 7x0.5 microphone cable. It comes in various colors, has the correct number of conductors, the diameter is correct (almost), the insulation is made of the same material, and it also has shielding, making it more mechanically robust!
Soldered in and looks like the original!!

Hello everyone,

Standard here, standard there, but for me, it was something else, something much more curious:

In the left taillight, one of the filaments in the dual-filament bulb (one filament for the taillight, one for the brake light) had melted in such a way that a metal droplet formed, which intermittently short-circuited the brake light and taillight circuit. As a result, the taillight was powering the brake lights, and the brake light was powering the parking light. Perhaps you can see it a little in the pictures.

http://www.drmahadevan.de/pics/birne23.jpg
http://www.drmahadevan.de/pics/birne24.jpg

Regards,
Martha.

Well, that's quite rare!

Thank you for the feedback!

CU Gremlin.

Crazy!

There is nothing that doesn't exist! ...