Number plate light not working

[checkmate]

Hi all

I have Audi A4 54 Reg

one of my number plate lights)rear ones) don't seem to work

I have changed the bulb and it still dont work. one of them works but other dont. Any ideas what this can be or what i should look for?

thanks in advance

[burkey1]

had the same thing and it was the bulb contacts that were poor.

Take out the bulb and check for 12v with a multimeter.

Im 99% it will be there..

If it is then get some emery paper and sand the contacts. I also had to pull mine out for the bulb to get good contact..

[checkmate]

hey i tried above and still no luck...is there anything else i need to look at?

[burkey1]

If there is no 12v at the contacts with the lights on then you most likely have a broken wire.

Take out the bulb holder and check for wire damage and 12v right at the wires.

[froggy72]

I had the same problem on my A4 1.9tdi and it turned out to be the wiring loom in my boot, the one by the hinge. Some of the wires had split which also stopped the boot from opening, I could only open boot with key. I had to get a new wiring loom as failed MOT coz of numberplate light.

[fourringsrus]

Well if the loom turns out to be damaged I would just run a new line from the lamp that works

[burkey1]

Ya as above. Your lights are in parallel.

See diagram (device X)

You can check for continuity on both wires to identify broken line and replace or just run a new line from good bulb to bad bulb and back again (as per wiring diag)

[haytch75]

Just done mine. Getting a decent contact was an absolute nightmare as the genuine parts I used seem to have much smaller contact areas than the originals I was replacing. I was determined to try everything to avoid having to mess about with wiring looms though and even considered tin-foil at one point!
If anyone wants a few stainless steel H3 allen screws then i'll send some out.