i have a 2003 vw passat 4motion and recently the heater stopped blowing hot air it just blows cool air even when i put the temp all the way up what could be wrong? thermostat? switch? its getting really cold where i live and need to get this fixed and usually do most repairs my self but this is frustrating me!! cause i cant figure out what it is, please help me!!!
Does the temp gauge move? Does it stay where it normally does? Have you checked to make sure you’re not low on coolant?
There are lots of possibilities. You could have a vacuum problem (maybe a hose with a split) or the thermostat is defective. I seem to recall that the 4motion model has an electronic temperature control, and that could be defective.
Do you have a CEL (Check Engine Light)? If yes, then: That CEL is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.