I have a 1996 850 GLT wagon with the two-zone electronic climate control where you set the temperature with the controller on AUTO and everything is supposed to control itself.

In 2000 we had situation where, gradually, the driver's side would blow nothing but hot air. We went to the dealer who first re-charged the AC. This didn't work. Next they tried to tell us that the driver's side Temp sensor was bad. THey replaced it, but that did not fix the problem. Then suggested that the AC evaporator was shot. Since this is a known problem with the 850, I believed them (and they might have been right). I had the (freakishly expensive) repair done and when I picked it up it seemed to be fixed. About a month later, however, it did the same thing - the driver's side produced nothing but hot air. I took it back to the dealer and they adjusted something (a fan speed) and it returned to normal. We hadn't seen the problem earilier, because it had been a hot summer, and it seems the system only had problems when it had to mix the air (when it just had to blast the AC it knew what to do)

All went well through the winter until I drove the car next Spring and discovered the new problem which is downright bizarre. The car would heat up to operating temperature and then the air temp coming out of the driver's side vents would oscilate between freezing cold and blistering hot continuously with a period (hot-to-hot or cold-to-cold) of 4.5 minutes. I can't tell you how annoying it is to have cold air blown on your feet on a cold spring day.

I don't know exactly when the problem started, because my wife typically drives the car, and she keeps the heat on max and blowing on her feet all winter.

I went back to the dealer, hoping that they might see this as a "tune up" of their (again, very expensive) repair. Not so, they hooked it up to the computer and got some error codes and wanted to change two temp sensors. My experience was that they would just start replacing things using my checkbook until they had found it, and I didn't want to pay dealer prices and $80/hour for that kind of nonsense.

Since the problem is predominantly expressed on the floor on the driver's side, I was wondering if they couldn't switch temperature sensors to see if the problem moved to the passenger side. This kind of diagnostic work is not their bag. I would like to make it mine. Has anyone delved into the ECC systems on these cars? Any pointers about adjustments I can make - or can't make?

Any help would be appreciated.

Steve