Klaus, thanks for the reply. I guess I should have posted in the c70 forum :)

Since yesterday, the compressor has refused to function at all. psi on the cheapo gauge reads 30psi. Nothing happens at all. Just blows very hot air, no clutch clicking no function at all.

I installed clips based on the broom handle diagnosis. The clips were flung out in rapid succession on the first try. I put them much more deeply in on the second try, but it looks like I've lost them again. It doesn't seem to be related to the click-on, click-off...

If critical pressure is 550 psi, then the system can take way more than I feared.

Guess the question would be... can you overcharge the system using a single can of R134a?


-----------Edit----------------
Okay apparently not. I emptied the rest of my 12oz can of R134a. ...must have been 8-10oz, since I added some yesterday and bled off the excess when I feared the pressure was in the red. Pressure never went above 40 psi with the clutch running.

After pumping new coolant into the system, the clutch kicked on and the lower pipe got quite cold. Cool air came out of the vents for a while, but eventually the clutch kicked off and stayed off.

So I'm back to where I started. Sounds like you have a similar issue. I read that there's a capacitor or somesuch on 850s that can be bypassed. I can't find an analogous part of my c70.

Any ideas of what I can do here? Could the preostat be the culprit?