alan8

I have a 97 A8. The HVAC is confused with respect to rest mode. Every time you turn off the engine it goes into rest mode. It will stay there for 10 minutes or so. You can turn it off immediately by turning the ignition to the on position again, then hitting OFF on the HVAC, and turning off the ignition again. At this point it will really be off - except, if you wait for 10 minutes it comes on again in rest mode (and runs for another 10 minutes). It also has a few other confused modes. If you do a few on/off cycles by hand (hitting OFF button and AUTO button) then cycle the engine off then back on again, the HVAC will sometimes be on, but not properly controlling temperature (e.g., if it should be cooling it will just run the fan on low).
In an unusual twist, if you disconnect the battery the HVAC will work perfectly for a day or two. So, somehow it is getting some memory and getting confused. Someone I talked to recently, who had done auto diagnostics in the past, thought the problem was with the body control system (?) - likely a sensor problem. He thought bad data might be coming in via a sensor confusing the control computer. When the battery is disconnected he thought this data would clear and take some time for the car to re-learn the bad data.
I have audi dealers and independents look at this, they have no idea how to proceed. The best they've been able to say is "this is normal" (not likely) or the HVAC is just doing what the computer is telling it to (they monitored the commands from the computer and said HVAC responded correctly).
Ideas?

PaulW

Did you hook up vag-com and see if there are any faults?

alan8

I'm no expert on this, but someone did read some fault codes for me. Used "OBDII Manual Mode?" It said there were two DTC's, P1136 and P1138, which seem unrelated. There were also several continuous and non-continuous monitor tests all of which either reported Complete or Not Supported.

Y888

i am getting similar problem,i turn off the car fan stays on,few days my sunroff didnt want to open after working good for 5 years,also my key is stuck in ignition but the fan thing started few days ago,i have solar sunroof,maybe i made it work because it never worked before lol

Y888

i managed to turn it off,somehow,turn on ac with engine on full blast pressed rest button that wont stay on turned the car off and now its off