A4 Headlight problem


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Jun 22, 2008
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Hello fellas, just visiting from the S3 section.
My pal has a 53 plate 2.5tdi A4 and he's got an issue with the headlights. The dipped beam has stopped working on both side while the main beam and side lights are fine. He has checked the fuses which are fine and it seams strange for both dip beam parts of both bulbs to have gone at the same time.
Could it be a relay?, any one any ideas or had this problem?
i thought that on that model the dipped beam bulb is a totally seperate bulb from the main beam and side lights,therefore it could be a relay or it is poss that it might be the switch as the first stage of the switch is the side lights and main beam is from the stalk on the steering column,might not be making a connection on the second stage which is the dipped beam.
are the front and rear fogs working?
Front fogs deff are working he drove to work on them and the sidelights
have you or your mate got a multi metre, unplug the switch and try belling out the contacts on the switch,or wait a little longer and someone on here with more knowledge than i will be along shortly.
i would also post this up on the a3/s3 section as theres alot more bods on there and would surley help out
Is the DIS saying the dipped beams are blown, if it was the bulbs then he'd get a warning on the DIS. Sounds like the switch or relay to me as well
It's a little more complicated than a simple switch and relay but still traceable with a Multimeter tracing the volts with respect to chassis........

The light switch is directly connected to the "Onboard Power Supply Control Unit" module (J519), which in turn supplies each bulb front and rear. The OPSC unit effectively is a big clever relay and bulb failure sensor feeding the DIS, as well as loads of other functions.

The main fuses that feed the OPSC unit are:
S36 = 30A
S37 = 20A (30A with headlight washers)


The light switch connections..... Switch Positions labelled: 0/1/2/A
Switch Common: Pin 15/30 = +12v supply (red) -from- J519:T32b/24 (without coming home lights / with coming home lights +12v supply from point A57??)
Pos.1: Pin 14/58 = sidelights [position 1] (grey) -to- J519:T32b/25
Pos.2: Pin 11/56 = dipped [position 2] (yellow) -to- J519:T32b/26

****T32b = 32 pin grey connector on OPSC.

OSPC Unit onwards:
The "dipped" connections out of the OPSC unit to the headlights are:
Dipped Beam (L)
J519:T23/23 (yellow/black wire) -to- T17a/16 -to- L Headlight connector 5/56b -to- Bulb M29

Dipped Beam (R)
J519:T23/22 (yellow/white wire) -to- T17ac/16 -to- R Headlight connector 5/56b -to- Bulb M31

The other side of the dipped bulbs are grounded.

****T17a = 17-pin red connector A-pillar left
****T17c = 17-pin red connector A-pillar right

It could be that your OSPC unit has gone faulty??
Perhaps possible to connect up to VAG-COM and see if there are any errors logged??
OSPC unit is "09: Cent. Elect."
Audi Part No. 8E0 907 279 ? ........ mine is version "B"

Hope this helps?
Evening all - Now then, did you boys reach a conclusion on this one? I've got the same story happening here
- Completely weird car working fine, left overnight at the airport. Returned to have no dipped beam.
- I've tried a couple of switches - but not luck
- No fuses, No bulb failure warnings
- Main, Sides & fogs all okay

The Haynes wiring diagram does seem to match the wiring on the switch, so thanks for the tips
- I'm a bit unfamiliar with Audis and your descriptions of terminal.
- If Haynes is at least part correct, I'd have thought I'd have lost other functionality if the X relay was out

I haven't got VAGcom -need to get sorted quickly (with the extra darkness at the moment).
Is this a CTRL+ALT+DELETE, or code clear thing or 'new unit - mate'
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An update on this - I've measured 3V at the input to the module... so something daft is going on.
Plan to unplug all other connectors to confirm I'm not having an issue with the internals of the module, but a wiring problem.
I'd buy a second hand CEM and that will probably fix it.
Replaced the OSPC unit with another (s/h) with the same suffix (C - supposedly A and E are also compatible) and guess what?
Yep - no change.
I can add however that I had no fault codes which I ran a Bosch diagnostic tool on it - other than inisting there was a problem with a rear door latch.
When I ran a systems test on the OSPC another surprise....no test for the dipped beam - rears, wipers, main and side but not dipped

Okay so I'm now struggling big time on this - does anyone have a good wiring diagram? or someone / somewhere in Essex who's good. The car's only usable in daylight - which is rare these days.

I've no bulb warnings and neither dipped is working - so can't believe it's the bulbs themselves, and I've had the wonky volts result - but I guess there's the possibility...
Hey guys I Have just bought an Audi A4 avaunt and it had the same problem as you are all describing so I had gone and put a new switch in thinking that it ŵas the most likely issue but made no differences however I continued searching for the issue and I found that the previous owner had put the head light bulbs in the wrong socket so I had swapped them around and now all works fine

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