fleetmgr

Well, for starters...you can't diagnose an A/C system using only the low side pressure, and if you're using the gauge on a can of gas you're getting what you paid for. The low pressure switch isn't there to allow the compressor to "save itself", it's there to regulate the temperature of the evaporator. The switch will, in normal operation, cause the compressor clutch to either engage or disengage based on load.

That said, you may be low on refrigerant. But, if you're low then you have a leak somewhere that should be fixed before charging.