A3 8P1 reverse light problems

A3 8P1 reverse light problems

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sheffieldyorky

Original Poster:

70 posts

57 months

Sunday 27th August 2023
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Hi there guys & gals
I have an Audi A3 1.9Tdi March 2009 8P1
I am trying unsuccessfully to get my reverse light to work.
Here’s what I know so far.
All the fuses are good both under the bonnet and in the passenger compartment.
With the rear light cluster out and the ignition on and in reverse there is no feed to that particular bulb, I used the “rear-view mirror”
I have replaced the “reverse light switch” with a new one not second-hand.
With the ignition on I have shorted out, i.e. a little wire link across the reverse light switch wiring harness plug and still no illumination.
On the fuse box cover ( inside the passenger compartment) the is nothing to suggest that there is a reverse light because the is no “reverse light fuse”.
On the rear light cluster, the rear light is supplied by a blue/brown.
Has anybody come across this problem before?
Reverse lights are not needed for an M.O.T. until car is registered after September 2009, but I would like to see where I backing up to.
I have had a couple of thoughts/ideas
Maybe the reverse light shares its circuit with another circuit, but that circuit is still working, which would signify a broken wire on the reverse light circuit.
Also, I plan to run a piece of wire from the "reverse light” plug under to bonnet to try and prove continuity at the rear light cluster


Belle427

9,570 posts

239 months

Sunday 27th August 2023
quotequote all
Broken wires usually occur in the rubber boot where they run from car to tailgate so im guessing its the most likely place.

sheffieldyorky

Original Poster:

70 posts

57 months

Monday 28th August 2023
quotequote all
Hi there
Many thanks for the response.
I have both clusters out and laid on the spare wheel cover, that was how I could observe anything through the rearview mirror, so no broken wires there

sheffieldyorky

Original Poster:

70 posts

57 months

Tuesday 6th August
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Now we have finally had some good weather and as my MOT is coming up on January 2025, I have set to and finally got around to sorting this reverse light problem once and for all.
So by process of elimination, I have found that the cable carrying the reverse light etc. is broken somewhere after the engine bay and before the rear cluster.
So without further problem, I ran in some new low voltage cable (similar to loudspeaker wire), once it was in I tested it for continuity.
With the reverse switch in one hand and my DVM continuity setting & leads in the other, I depressed the reverse switch and all was good.
I then ran a direct feed from the positive side of the battery through an inline fuse and then into the reverse switch (which was not in place at the moment) out of the reverse switch onwards on the new cable and finally connecting onto the rear cluster and reverse switch terminal (I had already found which track it was) went back to the engine bay and depressed the reverse switch which illuminated the rear light cluster reverse light.
I installed the switch and plugged it back in, ignition on and reverse selected no light, I then checked the wire on the rear cluster for a supply and nothing.
I took out the switch and on the vacant hole, I measured the distance with the gear stick in neutral and then with the stick in reverse there is a depth difference of about 3mm.
The brass plunger on the switch has a tiny (about 2mm across) pit mark or wear mark.
I can select reverse gear with a problem no clunking or clanking etc.
As stated here, I purchased a new reverse light switch on 27th August 2023, which is now just under 12 months old.
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So my question is as follows
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Is there an adjustment on the linkage to make the light work, to be honest, I don't want to upset anything and then not be able to select a particular gear.