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.
2000 Audi A8L 4.2
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.
Assuming this one is going into the trash why don't you cut it open so we can see those thingies that are the individual runs? I don't doubt they are there, but it would be interesting to see them all gunked up. Then maybe we can keep this thread for all the no heat questions.
A picture is worth a thousand no head threads or something like that.
When diagnosing my B5 A4ís heater problem, I experienced that both hoses connecting to the heater core were about the same temperature. It became clear the no heat transfer was occurring even though there was flow. After removing the core, I carefully removed the end caps. This is what I found:
The baffle between the inlet and outlet sections had broken. There is a bleed hole in the baffle. I assume this is to bleed air from the core by allowing removal of one hose. The hoses are at the top of the core. This makes me doubt the "air in the heater core" issue that is perpetuated on the forums...
How does air get traped below water?
The coolant was taking the path of least resistance. It was flowing directly to the outlet instead of through the core. Yes, the core was plugged. I doubt that any back flushing or chemical treatment would have cured that. Remember that the hose connections are at the top in the installed condition. Sediment doesn't really have much of a chance to escape once it enters.
Last edited by Old_School_Audi; 02-08-2014 at 02:28 PM.
This is a close up of the sediment found in the core. It is sand. Now the people saying you have to use the G12 coolant will tell you this happens because the wrong coolant was used. These are the same people selling the overpriced stuff. They haven't researched modern coolants and why the OEM uses it. High silicate water in Europe is to blame. The US doesn't have this. I use distilled water for mixing anyway.
I say this sand is from the engine block casting process. It's not unusual for sand to remain trapped in an iron block when it was made. This eventually works free and into other lower spots in the cooling system. That is the root cause.
BTW, I use the green Prestone in all my Audis...
Last edited by Old_School_Audi; 02-09-2014 at 02:46 PM.