Another heat issue...

[corystefanyshyn]

So I'm having issues with my heat, car is a 2004 ultrasport, all maintenance up to date etc

Symptoms:
-I can let my car idle for 15-20 minutes and the fan will still blow cold air
- after idling I can drive for 15+ minutes and the fan will blow room temperature air
- if I drive for a 20+ minutes or on the highway eventually the hot air will start to blow.
- engine temps are perfect
- no visible coolant leaks
- one thing to note, may be unrelated though, is that my center dash vents blow very minimal air, so little that I can barely feel it with my hand on the vent

I've read a ton of threads but am looking for some more specific insight, this is super inconvenient since the temps are starting to drop down to -30 degrees Celsius. Any insight would be wonderful! Thank you!

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[diagnosticator]

It is unlikely it takes 20 min of highway driving before coolant circulates through the heater core. Consequently, it is more likely the servo motors for the various air control flaps in the HVAC housing are sticking or not working. Do you have VCDS? If you do, then run an adaptation for all the servo motors by opening the HVAC controller and select block 001 then select Basic Settings, the set of servo motors will run to each end of the limits of travel and reset those values in the control module. This will often fix cranky servos, at least until it needs to be done again.

[corystefanyshyn]

It is unlikely it takes 20 min of highway driving before coolant circulates through the heater core. Consequently, it is more likely the servo motors for the various air control flaps in the HVAC housing are sticking or not working. Do you have VCDS? If you do, then run an adaptation for all the servo motors by opening the HVAC controller and select block 001 then select Basic Settings, the set of servo motors will run to each end of the limits of travel and reset those values in the control module. This will often fix cranky servos, at least until it needs to be done again.

I do have vcds, I will give that a shot. Thank you

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[corystefanyshyn]

Update: scanned with vag-com, no codes.
- flushed out the heater core and put new coolant in
- blead air from the hard pipe
- blead air from the upper heater hose

Some, but minimal heat now

The lower rad hose connecting to the hard pipe does, feel semi- pressurized and warm after a drive.
My lower heater core hose also gets hot after driving. But the top one is not pressurized or hot.

Any suggestions at this point? I've gone through tons of threads and tried to pin point the issue with no luck.

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