If the clutch is turning off at 25 PSI, then the low pressure switch is doing it's job. Why? Becasue R134a has a state change temperature of 29 degress F. What so special about that temperature? Water freezes.
So. If the AC cycling switch did not cut off, then the evaporator would FREEZE into a solid block of ice.
It is not possible to correctly charge a AC system without first confirming air flow over the inside and outside coils.
Anybody that gives you a set pressure number to indicate the system is full is giving bad advice. The pressure has to be corrected for the air temperature over the coil.
But assuming that the rest of the system is in good shape, then a low side pressure reading above 27.8 PSI is OK. Remember that it's better to be undercharged rather than over charged.
Refer to the following chart. http://seit.unsw.adfa.edu.au/coursew...frigerants.pdf