Passat Brake light unit

**AndyGlos** · 01-04-2009,04:41 PM

A bit of a strange one this..
The brake light on the drivers side has stopped working, while the rest of the lights in the unit are OK.. I've checked (and changed the bulb just in case), The connections to the unit are good and I've checked the wiring up to where it disappears under the seats and thats sound. The fuses are OK and there's no sign of burning or melting on the unit itself..

Have I missed something really basic here, because I'm scratching my head over this one....

**martin1810** · 01-04-2009,04:49 PM

Have you checked the power to the unit with a test light. Don't test with a voltmeter. If the wire is live then you must have an earth fault.

**AndyGlos** · 01-04-2009,04:53 PM

Thanks Martin. It seems a bit strange if it is an earth fault, that just one bulb is affected...

Where is the earth connection for that unit?

**martin1810** · 01-04-2009,07:04 PM

Brown wire on connector is earth for whole light so that must be ok if indicator is working but the bulb holders earth to this wire so a dirty/damaged connection between the bulb holder and the brown wire could still cause a fault. You can test this by running a jumper wire from a good earth straight to he bulb holder. This assumes you have a good 12v suply to the lght in the first place.

**AndyGlos** · 01-04-2009,07:29 PM

The rear light bulb is working, but doesn't illuminate the second filiment when the brakes are applied. I've swapped bulbs and its still the same. At least some progress is being made, oh and the 12v supply is good....

**martin1810** · 01-04-2009,07:37 PM

Don't forget it's two different 12v supplies, one for the rear light filament and one for the brake light filament. Do you have 12v when the pedal is pressed with ignition on.

**AndyGlos** · 02-04-2009,08:12 AM

Ah!!!!!!! Thanks again for that Martin. No I don't btw.....

**more power pls** · 09-04-2009,09:20 PM

hi I have the same problem on my 04 estate (tdi 130) did you find the route of the problem? Its mot time for me soon and I can see some blue scotch lock connectors comming out to play soon if I cant find the source of the fault!!

**AndyGlos** · 10-04-2009,12:08 PM

No I didn't. After much scrambling about I still couldn't find the fault. What I need is a vehicle electrical guru to come and ind the fault. My local dealer wants a kings ransom just for looking at it, let alone fixing it.....

Anyone have any other ideas?

**cazyp** · 10-04-2009,12:27 PM

If the 12v supply to the bulb holder is good when the brake pedal is pressed then the earth to it (to complete the circuit) must be bad.

Most of the bulbs in the unit are twin filament bulbs so can be swapped over when the brake light one blows.

Unplug the whole unit and give it a look over. Also check you're replacing the brake light and not the fog light etc. (Not being rude - easy to do.)

Of course it could always be a faulty brake light switch....