I'm in the middle of this with my '99 V70. Get yourself a 12V test light and clip the alligator clip to ground on the bottom of the engine. When the A/C has cut out, unplug the wire going to the A/C compressor and probe for power with the probe on the test light. (I did this from below. If you're doing from above, ground your light wherever it makes sense.) On my car, it lights up, telling me that power is getting through all the switches and relays, but the compressor clutch is not engaging. If you find this in your case, you will need to either replace the compressor or bypass the superheat switch. I haven't figured out how to do that yet, maybe I'll get to it this weekend. Basically, if there are two wires going inside the compressor, you want to splice them together. so that the power goes straight to the compressor clutch. On my car, I don't see any wires going into the compressor, but it may be hard to see without unbolting the compressor.