2001 xc70 damper gates

[importman]

Hello Board,

You have been great with other topics, you walked me through replacing my heater coil, but now spring has come and I need to tackle an a/c issue. During the summer time, the air blows cold but after 1 hour at highway speeds, it stops blowing into the cabin but it you can hear it blowing behind the dash. Its much like placing your hand over a hair dryer, you can hear it blow but nothing comes out. When it happens, I push the a/c off button, wait 10 minutes, push the a/c on button and it blows out cold in the cabin again. I have even let my shop idle the car outside in 90 degree heat for well over an hour and it blows cold the whole time, it only happens while driving. Could it be the a/c clutch? But than why doesn't it happen at idle?

Any direction would be appreciated.

[jimmy57]

Sounds like symptoms of evaporator freezing.
That car uses a temp probe stuck into evaporator case just above and right of accel. pedal.
If the sensor gets debris or dust on it it can become insensitive to the temp and the signal will not be cold enough for climate control module to cycle compressor off before evaporator freezes. Once it freezes the airflow stops that would carry the cold air across sesnor so it stays frozen and makes the noises you describe.
Idling the engine while diagnosing A/C problems IS NEVER CORRECT PROCEDURE TO FIND PROBLEMS OR CHARGE SYSTEM!!
(unless the complaint is specifically something that happens idling). It will not freeze idling since the sytem is working at much less than normal capacity.
The sensor could be faulty .

[importman]

I appreciate the reply. I am going to take a much closer look at it this weekend. I will let you know what comes out of it.