azaudi1hundo

I have a 1993 audi 100cs automatic. recently replaced the bulbs and checked the fuse and the reverse lights are still not working. any ideas would be appreciated thank you

Rusty Spokes

Question..Do you have auto mirror dip on your car? Is it working? With the button for the passenger side mirror pushed in, then put the car in reverse. Does the mirror glass rotate down (dip)?

azaudi1hundo

I am not sure if my car has auto mirror dip, i did try that, the mirror glass did NOT dip

Rusty Spokes

The reason I ask is a bad auto-dip controller will interfere with the BU lights. Surf the forum as there is a write-up about the controller.

azaudi1hundo

ok cool thank you

ncoupe

This may be an early warning that your transmission control switch is failing. This is a purely mechanical switch buried under the transmission, part of which controls that back-up lights. It is a clamshell design secured with rivets and the may start to rust out. The result is that some contacts inside the switch may not work properly. I do not want to alarm you unnecessarily, but if everything else ckecks out this is a possibility. Bad news, the switch is ~$600 if you can find it. Good news, you can fix the old switch, by cleaning lubricating and replacing the rivets by 2mm X 8mm screws.

I will look up the wiring diagrams to suggest other reasons for the problem, although my recollection is (I did this 7 years ago) that the circuit is pretty simple and although the switch closes the circuit for the auto mirror controller, they are in parallel, so I doubt RustySpokes's hypothesis, but I may be wrong.