i made a couple posts last year about my heater not working but i never really got anything resolved. i have a 97 A4Q with a 2.8L 12 valve motor. basically the heater doesnt blow hot air. i have done some researching and the main things i found were blocked heater core, heater valve control module, and the climate control module. well i checked both coolant hoses going into the heater core and they are both hot so i know the heater core isnt blocked. i then got under the dash and changed the temp from cold to hot and vice versa and watched the heater valve control module turn and push the the actuator out perfectly as it should. i have a new thermostat, water pump, and all that stuff so its not that. the system has been bled very well and i have never had any type of overheating problems at all so i know its not air in the system. so what else is there? i was reading about a vacuum operated flap that directs air over the heater core going bad alot, but isnt that the heater valve control module thats under the dashboard that i checked and works fine? i just dont know what else to check. and i cant seem to find anybody in my area with a vagcom to check for codes and stuff and i really dont want to take it to the shop for something that i can fix myself. if anybody has any information or has had this problem too, please help me out. its not even the heat that i really care about cause i live in charleston, SC and its only could a couple weeks a year, but i really need the defrost to work cause its been rainy lately, causing alot of window fogging issues. if anybody knows someone in my area with vagcom or has a list of people that have it, that would be a big help also. thanks

 

Its either your a/c control head, or the temperature blend door that directs air from the heater core to the air ducts. Either way a dealer tech should be able to find it.
P.S. its not gonna be cheap.

 

im not really wanting to pay someone to do it for me tho. is there any way that i can check something to find out for sure what is wrong? cause i would much rather buy a part and change it myself than take it to someone and pay out the ***. cause i was watching the heater valve control module when i changed temps on the AC control module and the motor turned on and the actuator moved and spun something else. isnt that the temperature blend door that your talking about? and if so, then arent both of those things working since the control unit made the motor kick on and actuate the arm to turn the flap (i'm assuming thats what it was turning)

 

There are about 4 flaps total, the temp blend door is on the driver's side in the back, you cannot see it.
The best thing for you to do is try and find a donor a/c control head to test out, if that doesn't work you might have to replace the entire hvac unit behind the dash.

 

sounds like that can be a pretty hard job huh. i guess i'll try and find someone that will let me use their control unit and try that first. any help on how to remove the control unit for whenever i find one to swap?

 

does anybody else have anymore suggestions or have had this happen to them? i have no idea where i'm going to find a donor AC control head unit cause i dont know anybody else that owns an audi, and i realy dont feel like pulling out my entire heater matrix and trying to find out whats wrong. does anybody know any way to narrow down whats wrong? what can i check to rule out some possibilities

 

i took a couple pics of the valves i found. the red one actuates anytime you change the temp. it opens and closes depending on how much air your asking for it to direct through the heater matrix to make hot. the blue one only actuates open and close. the only time it moves is when you turn the air compltely off or on. its always open until you turnall air compltely off, and then itactuates closed. bothof these valves are operating properly so that means the head unit is working properly as well, right??what else is in the system for me to check? as i said before, i have a97 A4 quattro with 2.8 12 valve motor. if anybodyhas any suggestions to check, i would really appreciate it. everything i have checked has been working properly so farand i dont know where else to look. its not a clogged heater core and its not water pump or thermostat. anything else thatwould make theheater not work?

 

can anybody help me out with this, as i have half my dash torn out and its kinda annoying driving to and from work everyday with wire harnesses and stuff hanging on my feet.any ideas or suggestions? i called around town and the certified audi technicians dont even have vag-com's so i have no idea what they use or where i can get a hold of a vag-com to use.

P.S. avant80@2.6 you have been helping me with this but it says that you cannot or will not accept PM's anymore, so i dont know if your inbox is full or whats up, but just thought i would let you know.

 

Ok so you already removed the battery and diss-connected the two heater hoses going to the heater core and blew it out with compressed air? How do you know its not a blocked heater core? You still cannot see what motor im talking about with that much of the dash torn apart, the whole sha bang has to come out.
FYI don't ask an audi technician what a VAG COM is, they don't know. Its a reversed engineered scan tool from the original VAS 5051/5052, they can do everything the VAG COM can and then some.

 

no i didnt remove the battery and blow air through the heater core. i fealt both hoses and they are the exact same temperature. i was told that if the inlet and return hoses from the heater matrix are both hot then the core isnt blocked, since the coolant is just as hot coming out as it is going in. am i wrong in this thinking? but thanks for the info about the vag-com tho, i was wondering why nobody knew what i was talking about.