I felt a cold shudder when I read this post. I picked up my 53 A4 avant almost a year ago to the day. My 'econ' light was permanently on.
Took the car back to Lincoln Audi and they told me the climate unit needed a new clutch unit. Courtesy car for a day. Car came back and appeared okay.
May / June 2008, the freaky hot weather started. Climate set to low, heavily pregnant wife in passenger seat. Warm air coming from the vents. Back to Lincoln Audi. New compressor required. Courtesy car for 2 days.
Car returned, air colder but not 'icy'. Still not convinced. Back to Lincoln Audi. Climate needed regassing and system checking for leaks. None found.
Few days later I was out with even heavier pregnant wife and 3 year old. Needed fuel. Could not open fuel flap. Returned the car home and it wouldn't lock. The alarm also went off sporadically throughout the night. Apologies neighbours. Guess where I took it ? Was told there was water ingress into the control unit under the passenger seat. Caused by climate drain plug being blocked by 'debris'. Was told the repair was not covered on warranty. Big argument ensued. Resulted in Lincoln Audi having the car for a further 6 days, replaced entire control unit, removed all carpets and had them dry cleaned.
Car seemed better for a few weeks. Then returned to tepid.
Took the car to Doncaster Audi, explained situation, paid £90 for a full regas. (couldn't be done through warranty ?????) Job done. Fixed. Icy.
I was told that had I not had the work done through my warranty it would have cost over a grand for the parts alone.
John, if its on warranty take it back straight away. If its not, get a second job.
Hope this helps.
Marcus.