Dr Dave
Platinum Member
Most R 134a systems use a low pressure cut off switch and a high pressure cutoff switch. If you are low on freon, they will tend to cycle on and off. So if it is shutting down, may be over charged, or condensor/ radiator dirty. Blow out and wash out, condensor and radiator cores. Also check evaporator core and cab filter, blow out if dirty. You can check an auto repair manual, for guage readings. R134a works best at exact charge, too much or too little makes a big difference. If you are low it is best to reclaim, evacuate air and moisture from system and add the exact charge. Look for a decal on or near a/c with charge amount, or check your manual.HF has cheap air powered vacuum pumps, evacuate for atleast 15 min.