AC works for about 20 minutes at a time
 

Earlier this year I had an evaporator core leaking, so I pulled the dash and replaced it along with the heater core. New accumulator/drier, orifice tube, vacuum and recharge.


Everything was great for a few months, but now I have an odd issue where the system will work fine for about 20 minutes at a time, then the compressor shuts off and system obviously goes warm. Let the car sit for a few hours, AC works again, for about 20 minutes, then off it goes again. It's like clockwork.

I need to check the charge but it has been doing this for about 2 months now, and it's not getting any worse, so I don't know that I'm losing refrigerant (but will verify with gauges).

Just curious if any of you have had this issue before? I've seen some chatter referring to an issue with the compressor clutch, but not understanding exactly what the failure mode is there and how it would cause symptoms such as this.

Thanks all!

I had a similar issue with the AC in my '99. did some troubleshooting and discovered that the compressor clutch just wouldn't engage after it got hot. Ran perfectly fine for 20-30 minutes like yours. then it would go to a mode where the clutch just wouldn't stay engaged. I took it all apart to try to troubleshoot but couldn't find a direct cause. I ended up putting a new compressor in (four Seasons from RockAuto).
You can check the clutch by putting 12 Volts across the two terminal connector. When you do that, you should see the clutch get pulled in by the electromagnet. I did find a clutch repair kit, but didn't seem worth the hassle for the price difference to a new compressor.
There doesn't seem like much to fail in there. It's essentially an emltromagnet that pulls the clutch plate in when it gets power. The magnetic force holds the clutch plate in and engages the compressor.

I took a shim out from the A/C clutch. If you take the nut off and pull the clutch plate, you will find a couple of very thin washers (shims) behind it that you can take out and close the gap a little bit. A very similar thing was happening with mine and that fixed it. You might have to work to convince the clutch plate to slip off but it will come pretty easily once you get it started. Might have to use a couple of thin bladed screwdrivers to wiggle it from side to side to get it started. Not much to it and it should work. My clutch is pretty worn and should really be replaced but this was a quick fix for me to get through the hot weather.