The symptoms that I originally reported have changed, probably my fault for noting them incorrectly in the first place. I said previously that the condenser fan was running all the time the AC was selected to on. Well it isn't now, it is not running at all, it should cycle with the compressor. The compressor doesn't have a visible clutch, later ones don't, but the end of the compressor is rotating. Another clue that I didn't notice before is that both condenser pipes are warm, not good, one should be cooler than the other. It points to a lack of gas pressure and hence probably a leak.
The AC was serviced three weeks ago and had been alright up until Tuesday so I don't suspect their competence, in fact they phoned me when they started on it that it was running cold enough and did I still want it done. I went ahead because it hadn't been for three years and it was possible that the lubricant included in the gas was getting a bit low.
Vic.