Listen to Larry - he has the right advice here. Before messing with the expensive, complicated stuff, check the simple.

First of all, you root cause very much appears to be that you are triggering the compressor clutch cutout. The speed sensor on the compressor is used to compare the compressor RPM to the engine RPM. Too much difference for too long, and the compressor is disabled until the car is restarted. If you can get the compressor going immediately by shutting off and restarting the engine, this is almost certainly your root cause.

Next, of course, is the question of why the cutout is tripping.

Start with the easy stuff. Clean the clutch surfaces. A little bit of slipping when the clutch engages is sufficient to trigger the cutout. Try giving the clutch a little more bite by cleaning off any residual oil/grease/gunk. Just spray your favorite degreaser into the air gap (engine off, please). Simple green, brake cleaner, Mr. Bubble - whatever. Wait five minutes, rinse a little bit with water, give it a try.

Second, check the air gap between the front clutch plate and the driven pulley. You're an old Porsche guy? Good - you must have a set of feeler guages laying around. As the clutch wears, the air gap increases, and the opportunity for slippage increases. The gap is specified at ~0.5mm. My anecdotal observation is that once it increases to ~0.8mm, clutch engagement will become iffy. If the gap is too large, you can purchase a kit to reset it from a good auto a/c specialty supplier.

Let us know if the clutch gap is too large and we can advise on procedure to reset. It's $5, 1 hour, and no need to disassemble & discharge/recharge the system.

- JimY