I just took my late 99 A4 1.8T to get the A\C serviced. A local shop hooked it up and added a little refrigerant. It still does not blow cold air. The a\c temp seems closer to ambient. The a\c tech said the a\c system itself is working because the a\c tubes are all hot and cold in the right locations. He suspected a problem in the air flap.

I dug around a bit behind the center console and monitored the flaps when I adjust the temp. There appears to be 2 motors, each linked to a red and blue lever that appear to work when the temp setting is adjusted. The Hot seems to make it hot, and cool seems to get "cooler" , but not anything close to cold.

Any help will be greatly appreciated.

 

How much is a little refrigerant? These cars can be finicky about the amounts of 134a in the system; too much and it won't run, not enough and it won't. You need to do some basic troubleshooting: does the compressor kick in and stay ON? Do the radiator fans also come on at the same time? Have you or the shop checked the pressure on the LOW side? With the compressor working and a full charge of freon, the gauge should read anywhere from 35-45 psi, depending on ambient temps (the hotter, more humid ambient the higher psi allowed).

 

Yep, and when you turn off the compressor, your pressure on the gauge (reading from the lines) should go up significantly (if the compressor works, and you turn it off, you're not compressing the freon anymore). If all that is OK, there's a decent chance the expansion valve in the system took a dump. That's what I suspect is the problem in my car. IIRC, the expansion valve is inside one of the hard lines in the engine bay, right up by the battery.

 

The tech connected the car to a a\c service system and it appeared to do everything automatically. He said the system took in about 1/2 pound of refrigerant. I will monitor the workings of the compressor and post my results. Thanks for the help.

 

do you have a outside tempature gauge in your cluster computer? i know if your tempature thermometer is not working the a/c will not blow cold...it will come on and everything but no cold air. for example my cluster temp. gauge said it was -35 degrees outside when it was actually 90 degrees outside....so my a/c gradually got warmer as the tempature dropped. it went all the way down then back up to normal temp and it started blowing cold air again.

 

If you have access to a real vagcom, you can check the HVAC module controls and flap motors.