[G-spec]

the compressor has to cycle like that or it'll blow the lines apart...there's a high pressure switch the dictates when to lock the compressors clutch and when to release. If the difference is that apparent when the compressors not running then your system may still be low on refridgerent.....OR could actually to over full, condensor could be shot, or the dryer, its hard to diagnose AC problems without being there with tools in hand.....best best would be to take it to a shop with a set of AC gauges and see what they say.