Hi I have a 2012 VW Passat that has a faulty Ac it will run perfect first time you start the vehicle Ac will run cold for 40mins then suddenly it goes warm will come back on for a few mins then warm again at this point you just have to turn it off, currently at my wits end Need help pls
The most common cause for this is a faulty expansion valve. The valve may be restricted causing too much cooling. This causes the evaporator to freeze over. Then the evaporator cannot let any cold air through. After awhile the evaporator thaws and it will cool the car for awhile until it freezes again. The pressures need to be tested with proper gages for a solid diagnosis. This should be done by an air conditioning specialist.