Compressor clutch kicking in but no gas flow might well be a blockage, quite common at the expansion valve. Need to get an air con engineer to connect gauges up to the HP and LP side which they'll often do free of charge as it only takes a minute. Then you can see what's going on
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Very high HP and very low LP would give the game away
Bicycle pump noises indicates gas isn't flowing steadily and the gas has to go through a very narrow venturi at the expansion valve which is easily blocked
Hmmm... so you think that it might possibly be the expansion valve then? That would be good as it's alot cheaper than a compressor!
I'll get it into my friendly garage to get them to look at it... unless anyone knows a decent automotive air-con specialist?