I've had this problem going on for a couple of years or so now, and finally ready to do something about it.  A/C will run cold for anywhere from a few minutes up to an hour or so, then the compressor will "slip out of gear" and the fan will just blow ambient-temp air.  I can eventually get the compressor to turn back on by toggling the A/C button off and on multiple times, but it takes anywhere from a dozen to 40-50 toggle tries to get it.  This happens regardless if I'm starting with a cold start, have been running errands around town (multiple stops), or extended highway driving. 

Any ideas, before I head to a dealer?

When it does this and you push the AC button on/off do you hear the compressor clutch "click" to engage? Do the cooling fans turn on?

 

 

Have you tried setting the mode to defog to see if the compressor engages?

I can usually detect when the compressor kicks back in.  I've used defogger but didn't notice if compressor engages.  I'll check that out.

I've had the same problem on my 2004 Forester XT. The best explanation / fix I've found is the magnetic clutch gap has worn a bit too much and can't stay pulled in. Adjusting the gap involves pulling the clutch plate hub and removing a shim to reduce the gap distance. I haven't tried to fix mine yet since I just rebuilt the engine after a spun rod bearing "event".

 

I'll try to find the link to post here. http://www.subaruforester.org/vbulletin/f87/how-adjust-c-compressor-clutch-116835

This is a different post than the one I had found before, but uses similar procedure and tools to do the adjustment.

Edited June 13, 201510 yr by Richard Young

Sounds like a A/C clutch going bad... My 03 Baja did the same thing. I was thinking it was a low charge because the compressor will cycle if low on charge or while charging until properly filled but after knowing I had a proper fill it would do the same thing but if I popped the hod and hit the compressor clutch it would allow the magnet to engage and work for a limited time. They are not hard to replace at all but you need to get the system evacuated of any refrigerant prior to any service of the A/C system.

Greg

I've read of people having bad a/c relays - corroded contacts drop too much energy or w'ever.