My compressor clutch disengages with the engine hot.
It generally goes like this:

Start car. Turn on AC. Clutch clicks on and off repeatedly. Car actually cools if I get on the highway fast enough, but never lasts more than 5 miles before it shuts off. AC doesn't work again until the engine is cool again. When it does work, it clicks on and off until it stops working entirely.

Did some exploratory checks on the system pressure, along with a partial bleed and recharge. The previous owner had overcharged the system, but I would get partial function even in that state.

I also confirmed that I needed to do the breadclip fix when I was able to engage the clutch by pressing it with a broom handle.

After the breadclip fix, I attached my pressure valve and ran the engine.

Compressor would build to ~40lbs and then would cut off. It would drop to 20lbs and would re-engage. It would cycle on and off until the engine reach normal operating temperature. At that point it would shut down and stay off. Most annoying.

I've bled off pressure twice now. Right now max is 30lbs, but it's too damn hot to run at all.

Write ups (VolvoSpeed and Matthew's Volvo) say that the shims are the usual issue. Constant on/off suggests low pressure. Pressure valve says that pressure is good, so I'm left with some faulty sensor sensor somewhere. I can't find any good info on a probably culprit sensor - except that there may be one. There are references to two sensors, but nothing concrete

Final bit is that this is a c70 hardtop, not an s70. Engine systems are the same. Folks (aside from Klaus) rarely read/post in the c70 forum and I really need some help here.