2003 A4 convertible. 90k miles. No prior problems except three years ago when a tensioner for the serpentine belt broke off and had to be replaced.

The problem started without any outside damage that I know of. I turned on the car one morning and a collection of electrical systems/controls no longer worked:

- The LCD computer readout in the center of the dashboard had switched to displaying the temperature in Celsius.
- All systems controlled from the steering column are unresponsive. Windshield wipers, high beams (can hold them on but they cannot be switched on), turn signals, horn, etc.
- Climate control. The temperature display LCD stays dark and none of the buttons respond.
- Power windows do not respond.
- This car has a turn switch to turn on the headlights. Pulling this switch out turns on the fog lights. If I pull out the switch the headlights start to rapidly flash.

The headlights works, the hazards work, and the radio works. The engine starts and runs normally. Power steering works.

There was a brief period (~5 minutes) a few days after the problem first appeared when everything was fine again. After driving for a short period, the problem reappeared and has been permanent since.

* * *

The internet led me to suspect the ignition switch. I got a new one and switched it out and nothing changed.

I brought the car to the local Audi dealer who contacted Audi. They were stumped. Their guess was the ignition switch, but I had already replaced it.

Their report reads: "Power fault found upon first diagnosis. Removed cluster and climate power module on power d/12 pin location and ground on d/13 pin location okay at cluster. s1 10a fuse okay, pin c/13 has power. checked j527 coding 2041 ok. contacted tech line and they would like tech to check comfort and op module for water damage. removed both no water damage. removed trim and wheel to get to ignition have all the powers at the contacts. tech also noted there is what looks to be water damage in the trunk. further diagnosis declined at this time."

Something interesting: This car automatically lowers and raises the windows when a door is opened so that the window will reseal with the roof. This function works fine even in the current state. This suggests that the windows are powered, although I cannot control them from the window controls. Perhaps this will isolate the problem.

 

The FIRST thing to check when weird electrical problems start are to check the grounding points on the wiring harness. There are several ground points located throughout the body. Ground straps connecting the engine to the body and the battery to the body. I'm not exactly sure where all of them are located on your car but I'd start there. Loosening the bolt that holds all of the individual ground lugs and retightening them seems to do the trick most of the time. If there is any visible corrosion, it will need to be cleaned off.

 

Alright, Dave. I'll do it tonight and see what happens.

I left the car in the rain last night and pulled up the carpet this morning to check for water around the CCM. Nothing.