Fuse for rear lights A4 B6 avant 2002

[glen40]

Hi, can anyone tell me what fuse manages the rear and front side lights on an Audi A4 B6. There is no fuse mentioned in the owners manual for these. Both front and rear are not working on the left hand side. I have taken both bulbs out and swapped them for the right hand side and they work ok there.
They do not work when I put the parking lights on either - ie move turn signal to the left when ignition is off. Moving turn signal to the right and the right hand side work ok.

Are there any in line fuses for the rear sidelights or do they go through some management gizmo!

I have disconnected the battery now and will see if maybe that resetts everything, you never know, works on computers doesn't it.

Would be grateful if someone could point out which fuses manage the sidelights

Thanks

[arman123]

I don't think there a fuse direct feed from on board power supply get a code read done see if any fault codes

[glen40]

HI, thanks Arman, I have done a code read and no errors.

Don't understand no fuse, why no fuses for sidelights, why have fuses for other items if that is the case or is it down to amount of power each item takes. Where does the feed to the sidelights come from and why is the left not working and right is?
Appreciate any guidance on what to try next.

[arman123]

You could check all bulb contact points check for corrosion water ingress in lights also have a look at your headlight switch that could be faulty and what did you scan it with? You need someone with VCDS to do a full scan on it

[glen40]

Thanks again Arman. The scan was with a VCDS, the only issues found are with Address46:Central Conv. to do with central locking 'Can't Unlock - Intermittent. Where would I expect to find an error for lights, at Address 09: Cent.Elec ? No fault codes found.

Checked the lights and no corrosion, the break light works fine (same bulb). Does the light switch have two connections, one for the left and one for the right, or is it possibly something to do with the 'magic' that sets the parking lights to left or right, that would maybe point at the indicator switch!

Some thoughts on how the power gets from the battery to the lights and connection from light switch/indicator stalk to lights would be helpful. Are there any in line fuses?

Thanks

[glen40]

hi, still not resolved this but reading Haynes manual note that there is an 'On-Board power supply control unit' that powers the lighting, washer/wiper, horns & accessory circuits. Can anybody advise on this, can I simply take it out and stick another in its place from a scrappy to see if that makes a difference.

[micheal balbrig]

Probably best to inquire at dealers or ask a good auto electrician for advice.

[GeorgeE]

Fuse 23 is side marker and tail light left hand side, I would start there.......

[a4cvt]

I had a lighting problem on my B6 1.9 tdI 2004. really strange things happened to sidelights and headlights but indicators were normal. I finally traced the fault to the on board power supply which was situated behind the fuse-box and under the steering wheel. If I remember correctly a new one was about £187.00 I bought a second hand one from the bay making sure it was exactly the same for £40. It worked perfectly.

[glen40]

Hi, thanks for advice however Fuse 23 is indicated as - Door (Rear left/rear right) on the fuse panel and I have checked all the fuses.
Any one changed an 'On-Board power supply control unit' , I have access to one from a donor car but do not want to mess everything up by connecting it. Haynes manual has just a few sentences explaining about unbolting etc so should be simple enough but it does also say 'noting if a new unit is fitted, it may need to be adapted/initialised using Audi Diagnostic equipment'. Could it be a relay or fuse on the power supply control unit, has anyone here taken one out, changed relays etc. Does anyone know what the relays on there are for, any info appreciated