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tamaz, Subaru master technician
Category: Subaru
Satisfied Customers: 1117
Experience:  Subaru certified,ASE Master technician,25 years experience
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My Subaru 2002 Outback H6 3.0 has an unusual problem with

Customer Question

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.
Any ideas?
Submitted: 3 months ago.
Category: Subaru
Expert:  tamaz replied 3 months ago.

Hi,there is a bulletin 10-74-02 which may help you solve this problem, it deals with the compressor revolution sensor there is a updated part .

Customer: replied 3 months ago.
VIN Number of my Outback H6 3.0 is 4S3BH8968 27653063, which is newer than the ones to which the service bulletin applies (up to 27645258), so my car probably already has the updated part.In reading the service bulletin, I'm not clear as to what this sensor is - a revolution sensor, or a temperature sensor, or both. The resistance test implies it is just a thermistor (temp sensor).Does an open sensor when overheated (if defective - intermittent) or open circuit due to connector failure, cause the controller to shut down the compressor? If so, that could explain my problem.Do you have any other ideas?Henry
Expert:  tamaz replied 3 months ago.

Hi,although your vehicle is out of the VIN range this does not mean the revolution sensor is not at fault here,there are a set of ohm values included in the bulletin,when its failing the resistance should be checked to make sure it's in spec,it's a easy and inexpensive diagnosis,thanks

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