Heating issue with car...

[p3u]

So it's been anywhere from 10 to -10 here in Colorado the last few days, and twice I've had my car fully warmed up, and when the fans should have been blowing warm air out, nothing! I then turned my car off, turned it back on, and heat started to flow. The other time I tried that nothing, but after a few minutes of driving it kicked back on.

Any ideas what could be causing this?

Thanks!

[TozoM8]

Audi is like windows. Sometimes you just have to reboot (clear the codes and see if they come back).

[4everRS]

These are some guesses:
I think the climate control unit works off of the coolant temp sensor as to when the blower motor kicks on and increases speed for heat. You may try to replace the temp sensor, but usually the guage in the cluster will also be nonfunctional.
The only other thing I can think of is that the climate control unit is bad.

The sensor is so cheap, I would try that first.
Disclosure: I may be way off base with some of these assumptions. Had a 99 a6 that had climate control issues and the temp sensor was the culprit.

[AudiRS4ever]

It sounds like a final stage unit on a BMW. They go out all the time. My M5's was constantly getting replaced, because of the same problems you are describing. I don't think Audi's use anything like that though. If they don't I would think it's your HVAC control unit, or maybe the blower fan is getting stuck and not spinning. Does the control unit show a fan speed with no air coming out, or is showing no fan speed?

[p3u]

It sounds like a final stage unit on a BMW. They go out all the time. My M5's was constantly getting replaced, because of the same problems you are describing. I don't think Audi's use anything like that though. If they don't I would think it's your HVAC control unit, or maybe the blower fan is getting stuck and not spinning. Does the control unit show a fan speed with no air coming out, or is showing no fan speed?

The fan would still blow air, but no heat....:vgrumpy:

I did notice my coolant was a bit low, and got a notification for it today. I topped it off, maybe that was the issue? Time will tell I guess.

[AudiRS4ever]

Hmmmm....... if the fan was blowing the speed that was showing in your control unit it shouldn't be your control unit. Probably coolant level (best case) or could be a clogged heater core (worst case). 10 to 1 says just low on coolant.

[Amulet-S6]

Mine has done the same thing very sporadically over the past two winters.

[uberrs6]

Any codes? The flapper door motors in the HVAC will code a fault if they dont open or close properly.

[Innovator]

Hmmmm....... if the fan was blowing the speed that was showing in your control unit it shouldn't be your control unit. Probably coolant level (best case) or could be a clogged heater core (worst case). 10 to 1 says just low on coolant.

Heater cores are known to clog on these cars and Audis in general. You can use compressed air and hot water to clear it out, but you must go opposite the direction of normal flow.

[p3u]

How would I go about cleaning out the heater core if it was clogged? Location?

Thanks

[Innovator]

How would I go about cleaning out the heater core if it was clogged? Location?

Thanks
You need to remove the entire dash and the heater box.