Nissan Repair: 97 Altima intermittent A/C sys, ant tips, valve system

Question
Von,
My Altima has +200K. The car AC works good for 20 minutes and then starts blowing very warm air off & on. I don't think the compreesor is cycling. I never had a problem till now with the A.C sys. Ant tips for troubleshooting.I do some electronics for my career.

Answer
Barry,

You will need to check the system pressures to be sure.  But, for the record here are the things that can cause this.  First, if the compressor cuts off look at the compressor relay and the pressure switch.  If the compressor stays on and the system gets hot look at the expansion valve.  System pressures area key to understanding what is going on with the system.  Get an airconditioning book from Haynes at your local parts store and look up your model for the system pressures.  Book is $20 bucks and a set of gauges are around fifty bucks.