AC Blows Cold Air Only When Driving 30 MPH or Faster

pdemit

The AC on my 2008 2.0 L turbo now only works when I am driving at speeds of at least 30 MPH. When driving at slower speeds or idling, the AC blows warm air.

I brought car to two VW dealerships to have their service department diagnose the problem. When running diagnostic on AC system, it states that their is voltage to the compressor but the compressor does not turn on. The freon level is good and system has no leaks. VW suggests replace compressor, expansion valve, drier and condensor at cost of $2,225 but made no guarantee that problem will be fixed. VW technicians with whom I spoke do not know why the system works while driving at 30 MPH or faster yet blows warm air at slower speeds.

I would greatly appreciate any insights or suggestions before I spend $2K+ in the hopes that it will correct the problem.

Thank you for your assistance.

Mr_Shiftright

I wonder if your cooling fan is operating as designed--if your AC condenser up front is not cooled properly, you will have symptoms like this. Or if the refrigerant pressure switch isn't working right, that might cause a random operation of the AC compressor clutch.

I'd suggest you visit an AC specialist who may be able to diagnose this properly. The suggestion to replace every conceivable piece in the AC system, and then not stand behind it, sounds like a very bad idea to me on any number of levels.

slinger1

I agree with MrShift@Edmunds, same thing happened to a friend of mine with a Honda CR-V. Hers would cool fine while driving around and then turn warm at idle. I replaced both engine cooling fans (they were not operating even when I connected them directly to battery power) and that solved the problem. Some cars when the engine cooling fan behind the radiator doesn't turn on it won't let the compressor turn on as it would make the engine overheat. Maybe you can check under the hood at idle with the A/C on and visually look to see if the fan is turning. If not, there is a problem with the fan circuit or the fan itself and you will have to have a shop look into that. Hope this helps!

pdemit

Thank you for your comments. These are very helpful and confirmed my instinct to keep looking for a better alternative to replacing the whole system.