My air conditioner in my Jeep has recently stopped working correctly. It only blows warm air. I originally suspected that I was low on Freon and topped it off. After topping off the freon the air blows cold for a few minutes then goes warm again. Also, the freon level never reads low. Someone has suggested relpacing the “low pressure switch.” Can anyone explain what the low pressure switch is and is this possibly something I can do myself?