The evaporator temperature sensor can fail, causing the AC compressor not to cycle. If the AC compressor does not turn on, the AC system will not blow cold air. If the compressor is stuck on, the air will be very cold at first, before warming up.
Car Problem Reports
Mercedes-Benz S430 Evaporator Temperature Sensor Failure
Mercedes-Benz S430 Problem
Average Mileage: 78,000 mi (50,000 mi - 106,000 mi)
Visitor, 2003 Mercedes-Benz S430, 50,000 mi
Fixed my AC for $3000 a year ago. Now I have similar problem again.
air conditioning works only sometimes. Had unit fully charged. Air only worked sometimes. Brought to Mercedes dealer. Found faults in system. Dealer corrected them. Picked up car after Mercedes said it worked fine. Next day air did not work. What to do ?. Now there telling me it might need an air conditioning control modual. Now I have to drive another hour and 15 minutes to my Mercedes dealer in Hartford Ct. Not happy that this wasn't corrected the first time I brought the car in for repair. Thought Mercedes dealers were better than that.