99 Hyundai Sonata AC problem continued
 

I accidentally cut my last post short. AC works intermittently. It is a
V6. I believe the compressor is OK because it only stops working when the
AC clutch is not engaging. Do AC clutches start to fail with intermittent
action or do they just quit? Seems odd that it works great sometimes then
not at all next time you start the car. Any advice??? Thanks in advance.

Re: 99 Hyundai Sonata AC problem continued
 

Your A/C system has both high and low pressure switches. Being either
over- or under-charged will cause the compressor to shut off.

You also have a thermistor in the evaporator which will shut off the
compressor.

It's also possible that the ECM will shut off the compressor under heavy
throttle. I haven't checked your particular car, but I know this system
exists on many Hyundai products.

If you're unsure whether it's the compressor, connect a test light between
the compressor electrical connector and ground. Lamp off means the
compressor's receiving no power to engage the clutch.

Re: 99 Hyundai Sonata AC problem continued
 

Thanks hyundaitech. I appreciate your input. It sounds like a good idea.
I'll give that a try.