My Subaru 2002 Outback H6 3.0 has an unusual problem with the HVAC. The AC cuts out (ceases to blow cold air) after about 1 hour of driving on a hot day (30C/86F). It used to require several hours of cool down before it would come back. It works fine at more moderate outdoor temperatures and in winter.
After replacing the car battery
last week, the problem changed a bit. Now the AC worked again after just a short (gas fillup) stop.
When the failure occurs, cycling the HVAC on/off has no effect on the problem. Changing the temperature setting affects the fan speed, but does not bring cold air back.
This problem started about two years ago.
Refridgerant pressure has been checked & double checked. It is OK. Compressor works normally, but hasn't been checked when the problem occurs - due to never being near a dealer when it occurs!
Another wierd symptom - the interior AC/Heater fan momentarily cuts out on hard right turns, just for seconds during the turn. This problem also seems to be less likely since changing the battery. Dealer claims to have checked for loose cable connections - found none. Wants to sell me a new fan motor.
My theory is that there is a sensor under the hood that is both temperature and battery voltage sensitive - and cuts out.