Aircon cool air flow closes off in cabin after 20 seconds

something you need to ask , technical help here.

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revtastic
still on the production line
Posts: 10
Joined: Mon May 26, 2014 10:44 pm
Passat model: B6

Aircon cool air flow closes off in cabin after 20 seconds

Post by revtastic »

I have a strange aircon issue where cold air flow in to the car interior stops after about 20 seconds. If I turn the air con off (with the off or econ button) and then back on again I get cold air for another 20 seconds and that's how I've been keeping cool in the recent hot weather!

When I turn Econ on (which turns off the aircon) the air flow to the car interior immediately goes back to normal - just not with cold air.

Both of the cooling fans in the engine bay run as expected when the aircon is running.

I took my car to a local aircon specialist and he diagnosed a faulty compressor. I've just had the compressor replaced and still have the same problem. The aircon guy is stumped and is 'investigating the fault' - that was 2 weeks ago now and still no diagnosis..

I thought it might be the aircon / heater control unit in the dashboard so replaced it with a working second hand unit off eBay - no change.

When the cool air flow to the car interior stops you can hear the flow die down inside the car and it sounds like the blower is still going full pelt behind the dash. It seems to me like a vent is shutting off all air (cool) flow to the car interior after 20 seconds.

I'm thinking maybe a faulty sensor somewhere that's wrongly telling the system to close vents to the car interior?

Has anyone else experienced this weird fault and have any ideas as to how I might be able to fix this? It's really frustrating. At the rate I'm going I'll probably miss the hot season completely.

I'm not sure what to check next. :sad:
B6 2.0 TFSI, R-Tech Stage II+ Custom Map, BCS 3" Downpipe (no pre-cat), Revo Intake System, Audi S3 FMIC, Uprated HPFP.

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