Interior Illumination switch not working. Common problem?
 

First off, hello. First time poster, long time lurker. Through the numerous Audi forums, this one has always steered me right. Kudos.

I always wanted a B5 A4 since I was ten years old. I finally bought one in August, and noticed the illumination switch was quite touchy, sometimes even a pot hole or speed bump would rattle it loose from full brightness to less than half. It also seemed to set the brightness as the 12 o'clock position of the dial, spinning left or right would just dim the lights.

I replaced my spark plugs, after my first 10,000 miles, and got back in the car and drove to work. At night I noticed the illumination was less than 1/2, i tried to turn it up and just spun freely, not changing the brightness.

At first i thought the switch was fried, but it still pulls out from its stationary position and clicks in to reset the mileage. I have the repair manual, I just don't know how much of a project it will be or if it will be worth it, if i can't fix the issue. I figure the pot might just be bad, or the spark plugs would cause this?

Thanks in advance and any insight at all is appreciated. Is there a reason for this, or is it notorious to wear over time?

Sounds like the pot to me (def not the plugs), or the connection between the plastic dial and the pot. I havent heard of this problem personally, but I would pull the cluster (really easy to do, two screws where the cluster meets the steering column, you can google it), and see if you can mess with it, I would think you have a shot since you know what a pot is. Otherwise you could get a new cluster, but that seems like overkill..

And BTW your repair manual wont help at all, this problem is too "low level", the repair manuals recommendation would be to replace the instrument cluster.

Wow. 4 screws and some steering column brackets is no problem. Thanks a lot.

Still a newbie when it comes to the A4, being used to working on domestic cars. I panicked a bit when the repair manual's solution called for entire dash removal.

I will have to do this tonight and keep you posted. Thanks for the props on my knowledge of pots. Hah.

My LCD display is different, only showing the attention icons (trunk, gas, etc) but bolts the same. (For anyone else having the same problem):
Instrument cluster removal - Audi A4 S4 A6 - YouTube