A3 Electrical Problem

[DavidGB]

Hopefully a very simple question requiring a simple answer

Noticed that the rear left (kerbside) brake light wasn't operating so changed the bulb but that didn't help.
Both bulbs (the one I removed and the replacement) are ok.
Indicators are operational.
Fuses seem ok (??)
Where to go next I wonder.
Any thoughts ???

 

[DavidGB]

Perhaps not such a simple question after all as no-one seems to have responded.
Having a look through the fuse boxes now but there doesn't seem to be an adequate guide to what fuse does what.
The layout doesn't agree with what's show in the drivers manual.
Is this typical of Audi ?

 

[Geraldy212]

David, as far as I can see from the wiring diagram that I have, there are no fuses for individual stop lights. You could try measuring the voltage at the lamp contacts to see if you are getting 12 volts when the pedal is pressed. If there is any voltage at all, the circuit is intact. What I suggest is that you take a close look at the bulb holder for signs of corrosion. Clean the contacts anyway. If OK, check the wiring and any other connectors you find. See if this does the trick. Good luck.

 

[JPK]

Have you got a 'left brake light' warning on the DIS?

Also, have to say it.. But you definitely changed the correct bulb?

 

[Dannykn9]

Possibly a brake in the wire mate.
check all the the wires going to the cluster and make sure they are all firmly in place, with no brakes in them.

 

[plymouthaudi]

I had the same problem on the right hand side rear light. It was a plug in the foot well near the OBD port well behind and up of this. There will be a connector block with about 6-8 plugs in and a red clip to hold them all in. One had some how disconnected itself and cause all sorts of problems. put back in and problem solved. If it's not that then maybe you have a bad earth inside the light cluster or on the cable going to the cluster or water inside. Hope this helps.

 

[DavidGB]

Just spent a chilly hour outside trying to see if I had missed something.
Don't think so.
The lamp contacts are clean and lovely.
The connector is like new and well seated in the lamp housing
The wires (as far as I can trace them) look faultless.
There is no voltage appearing at the stop light socket when the pedal is depressed but the right hand brake light and the high level light work fine.
Interestingly the kerbside parking light doesn't work on that side either. (That's the light you can use when parked up at night to illuminate the car on one side only - it's actuated by the indicator switch).
Um yes I did change the correct bulb ! But have to admit that's not such a daft observation - sillier things happen. Anyway the bulb I took out was fine anyway.
Warning light on the DIS ? No.
Break in the brake light wiring ? Well if there is I can't see it and wouldn't know how to begin to find it if it's hidden back in the wiring loom.
So tomorrow I'm going to call the German Motor Company in Wandsworth, London to see if they can connect me to one of their computers as I'm beginning to think that the answer to this irritating problem lies somewhere in the befuddled brain of my Audi.
I never had this problem with my Morris Minor - could always locate faults and fix 'em, even by the roadside.
Is this the Germans trying to get their own back after that World Cup win back in '66 ? Or does their hatred for us go back even further ?

 

[DavidGB]

Hi Plymouthaudi<br>Now that's interesting.<br>A connector block near the OBD port (???? whatever that is ????)&nbsp;<br>Can you be a little more specific ?<br>Don't mind going out into the cold once more if I know what I'm looking for.<br><br>

 

[plymouthaudi]

Sorry mate I will try and explain better. If you look at the steering wheel underneath you have a plastic cover, it has the coin holder and all the light switches attached to it also the OBD port and footwell lights are attached to this cover. It's fairly big. To undo this cover take the fuse panel cover off which is located on the drivers side. Then u will see a 8mm (I think) bolt, undo this also if u look near the OBD port there will be another 8mm bolt and also to the far left another Undo all these and remove the cover disconnect the OBD plug and also the light switch and dimmer plugs ( if u have footwell lights this also) then the cover can be removed being careful of the clips holding this in place at the top left and right which are onto the dash. Once this is out the way if u get your head Into the foot well and look directly up u will see a connector block with a red clip or clips. And there will be either 6 or 8 plugs. If u check they are all secure and no cables loose chaffed or any insulation broken down and shorting to earth. That was my fault and once repaired or plugged back in should be good to go. It's worth a check to say the least. Hope this helps.

 

[plymouthaudi]

also the OBD port is where you will plug in vcds or any other fault diagnostic tool.

 

[DavidGB]

Thanks for your very thorough explanation and I'll have a look at that first thing in the morning.
But now for Sunday Roast !

 

[plymouthaudi]

No probz mate let us know how u get on, And Nice I'm jealous working away no roast for me!!

 

[plymouthaudi]

How did you get on mate or have you not had a chance to have a look yet?

 

[Ash187]

use the first part of this guide to get in to the CEM (the part that Plymouthaudi is trying to explain)

Fourtitude.com - BiXenon Wiring & Coding

 

[12sec1/4]

Thread revival...

I have this issue. Also on the dash I get the error. Lamps are fine (cheap halfords) and connections are not corroded.

Would be good to know how the OP sorted it.