Questions and Answers

Mercedes Benz E420 HVAC Not Cooling Q. Hi Vincent, I own a 1999 Mercedes Benz E420. The car has undergone periodic maintenance and is in a very good condition. Just recently I started experiencing problems with the air conditioning of the car. When I first turn on the car, I get cool air for about one minute and then it's just the uncooled air from the blower fan. When the cooling is functioning, the temperature control works fine.

When the cooling stops, lowering the temperature appears to be having an affect on, I believe, the compressor clutch, blower fan speeds etc., but no cooling takes place. It appears that the condenser is being commanded off by the ACC? Any Ideas as to where the problem could be?

Thanks in advance,
Vimal

A. There was a TSB issued to address this problem. It seems condensation water is damaging the Evaporator Temperature Sensor (ETS) and shutting down the A/C. Shutting the car off and then restarting will get the A/C working again and then shut down again. Your Mercedes Benz dealer will be able to confirm this.

Other than that, the most common cause of the problem you describe is low freon level in the A/C system. The Automatic Air Conditioning (AAC) has a self diagnostic function and will store DTCs. However, you will need the Mercedes Benz HHT to access them.