Fan Cycling Problem.

[Chamberpains]

Most AC pressure switches can be changed without evacuating the system. Including the high pressure fan switch. They have Schrader valves like the valve that's in your valve stem in tires, behind them. I say most because sometimes you will find somebody will rig one together because the Schrader valve was shot and not put a new one in or they will sometimes stick. It's always a possibility. you'll get a little Spurt of freon that comes out but that should be about it. Keep your hands away from the freon it stings a good bit on bare skin.
Yes, switches do go bad where they flicker intermittently. If you checked the wiring thoroughly and the plug checked out. then I would suspect the switch is shot.