My '91 legacy has 175K on it. The AC has never been serviced.

Over the past 3 years of operation the unit has become intermittent. Its as though it has a mind of its own.

Typically, in the morning, when I go to work, the AC is reluctant to come on. Sometimes I'm a mile from the job before it decides its time to cool the car. Other times it may kick on almost immediately and remain that way or go instantly back off. When it does come on, it cools the car as it did when new.

When I go out to lunch and the interior of the car is hot, the AC comes on 100% of the time and operates great all the way to my destination. When I leave my lunch stop to return to work, however, the AC becomes more iffy. It may come on immediately and work fine or have a delayed start and operate intermittently on the way back to work.

Occasionally, I get into the car and drive it for 20miles and the AC works perfectly. Any suggestions?

You should have it checked out by an AC shop.

 

You can also check the wiring going to the compressor, and various other AC components for wire that's rubbed through, etc. You may also want to unplug and plug in the connectors at the compressor, pressure sensor, etc. There might be a bad connection somewhere.

Along with Josh's suggestions I would look at the relay for the AC, it may be intermittent. If you want to work on this yourself I would invest in a service manual for the car.

My '91 legacy has 175K on it. The AC has never been serviced. Over the past 3 years of operation the unit has become intermittent. Its as though it has a mind of its own.

Wow... this is an old thread but I am having the exact same symptoms in my 2001 Outback. It's totally unpredicitable when it works and when it does not. It seems the compressor is just not kicking in. I hit the A/C button, it goes green, the idle gets bumped up a bit but you can tell the compressor is not engaging. Then other times, works like a champ. I'll have to see if the compressor is getting the correct control voltage.