Have a 2007 jetta. A/C works well. However when highway driving the air stops blowing into cabin as if someone had shut all vents. When slow down, problem goes away. Took it to dealer and they have no clue. I need help.
Sounds like a vacuum problem: If the HVAC uses vacuum actuators to direct airflow, a low-vacuum situation (e.g. a leak that shows itself when the throttle is open) causes the airflow to return to the default, which is the defroster vents.
Does it come out anywhere else? Defrost or heater?
They used to use vacuum operated windshield wipers, bad idea.
Thank you for comments. Took car to mechanic who stated that a valve stays open and the system freezes, which is why air stops blowing. When ice melts air flow reestablished. Solution, new compressor. About $2,0000. Have not done it yet. What do you all think?
Why a new compressor if the expansion valve is sticking? The exp. valve is under the dash with the evap coil. The compressor sounds like it is working fine. I’d get a second opinion.
+1 to BustedKnuckles’ comment.
I strongly recommend a second opinion, and I would recommend that this opinion come from an automotive A/C specialist shop, rather then from a regular mechanic’s shop.
Your regular mechanic may be fine for most problems, but when it comes to things like A/C and automatic transmissions, I think that a specialist is preferable. After all, when you need surgery, you don’t have it performed by your family doctor, so in a similar fashion, you should seek a specialist for your A/C.