Nissan Repair: Air Conditioning, hall effect switch, pressure switch

Question
Hi,
I have a 1991 Nissan SE V6 pickup. Recently the air conditioning has been acting up. It will cool for a few minutes then the temperature will increase as if it has been swithed to vent and after a few minutes it will start cooling again. When it oools it works great. If I turn the AC ON an OFF it will start blowing cold air again. What do you think I should do to fix the problem.
Thank You!  Matt

Answer
Matt,

Check to see if the hall effect switch on the compressor has loosened up.  It is a device that bolts to the outside of the compressor and lets the computer know that the compressor is on.  If the distance between the sensor and the pulley clutch becomes too great it will turn the compressor off.  Other causes are an overcharged or undercharged system or lastly a defective pressure switch.  I would check the sensor first and then the system pressures.