Seem to remember someone describing a scenario where he got cooling when starting for the day but then once it cut out he never had AC again till car had cooled down.

I have positively identified the "fault" to the internal switch by connecting my LED test lights while driving. One light to the AC relay output pin and the other to clutch wire. When compressor cut out I had 12V at the relay output but not at the clutch. I keep in mind that accumulator pressure switch is not in this part of the circuit as on other cars. The relay is the final output to the compressor. Further testing revealed that the internal switch was open. Cooling for a while allows the switch to close again. In fact pouring a bit of cool water on the compressor shell near the switch wires closed the switch almost instantly

Your explanantion of the 3 stage linear switch on the high side makes perfect sense, thank you, always wondered about that. I always thought that those square boxes were a heat sensitive switch. It is connected in series to the clutch and is always mounted as if to pick up the heat in the compressor body .

So it seems that there may be some redundancy in the system to protect the compressor from overheat/overpressure. I suppose this redundancy would arise because different compressors that Volvo use may or may not have an internal switch. Your comment that I may be overcharged holds water because I topped up the freon last fall by trial and error (ie I topped it up until it cooled and got some cycling of the compressor at higher RPM). But it was done on a much cooler day. I suppose the best plan would be to bleed a bit of freon out and then continue to monitor that switch. I really do not want to drain and refill according to weight because I have no real way to do that. What do you think about bypassing the internal switch (assuming my theory is correct about the square thingy and therefore having some redundancy).

PS: Canadian?
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David Hunter