Hello, I have a 2001 a4 1.8t with 120k miles and my heat is not working at all. Last winter it worked fine and the ac was fine all summer but now I have no heat. Being that its only 5deg out this is a serious problem, my defrosters don't do anything, I can barley see to drive. I have done a lot of googling on this issue and every thread ends up a dead end. It seems to be most likely that it's either the blend door or the heater core. My car heats up to normal temp, both lines going to the core get hot, no smell of coolant, and nothing has been done to the system since last year when it worked. all the controls seem to work fine on the dash but I am getting 0 heat. Is there a way to test the blend door? If so how would I go about doing so. Any ideas or advice would be greatly appreciated.. this is becoming a dangerous situation with no defrosters. if it is the blend door is there a way to manually move it to heat till a more permanent fix can be done?
My 2001 A4 did the exact same thing. The best and easiest thing to do is flush the heater core with just regular clean water from your garden hose. Flush it several times with water then get you some CLR and pour it into your heater core until it is full and let it sit over night. The next day flush the core several times more to make sure you get all the CLR out. Each time you flush you need to blow the water out with air (but not to much pressure as you could damage the heater core) to dislodge anything that might be clogging it. You will probably see calcium deposits come out of it witch is probably the issue. I put a five gallon bucket next to my car with the hose ran to it so I could see what was coming out. Hopefully this is your issue because the dash needs to come out to fix the blend door. Good luck!
If you check faults and there are no temp flap codes than the heater core is bad. The blend doors are very stout and the blend door actuator is rather weak so if its the motor, and the system does not see the position sensor for the heater flap move, so it sets a fault code. I will try and get a picture of why the heater cores plug up and what they look like. You can try flushing, rarely works. Replace the heater core is the long term most effective solution.
1991 Audi 200 Turbo
1999 Audi A6 Avant 2.8
1998 Audi A4 quattro 1.8T
How do I check for faults? I dont have access to VAG COM. Also, what confuses me about the heater core is if its clogged wouldnt one of my lines not get hot? After the car is warmed up both lines are good and hot. One is not hotter then the other, seems like coolant is passing through the core. I had no tell tale signs of the core going out. No coolant smell, fogging windows, never worked when I was at higher RPMS, just the 1st time I tried to use the heat I got nothing. If it's clogged will both lines still get to normal temperature?
I thought the same thing with both lines being hot. I figured if it was hot going in and hot coming out then it was not the problem but I just got tired of trying to guess and flushed my heater core and ran the clr anyway. After I did that I have heat again so it's definitely worth a shot and it's cheap.
Ok so I checked again and both lines are hot.(which confuses me to it being the core) I did add some coolant and I think it may not have been G12 (it was pink VW coolant back in the summer) could that have contaminated the system and clogged the core? The coolant was pentofrost++ http://www.pentosin.net/specsheets/Pentofrost_++.pdf now that I read it it says 06 and up. I checked by recirc door below the cabin filter, it works when I hit the recirc button. Also, if I put my temp to low with low fan speed then raise the temp I hear a I hear a click that I am assuming is the blend door functioning correctly. I posted the spec sheet for the coolant I added. Could that be the culprit that clogged the core? Thanks for any help. Once I get this resolved I will post the steps I took so people can use this for future reference. Thanks.
UPDATE: Apparently even if both lines get hot, somehow your heater core can still get clogged. Turned out to be my issue.. I did a half *** flush with a funnel, bucket of water, and a vinal line. Id pore some water in the line then blow it through with compressed air. I plan on doing a better flush when it's not 5deg outside. But even the half assed one worked. I have heat, not as hot as I remember but I have heat. Next is to drain all the coolant and replace then flush again.