I was driving my car tonight and smelled something burning. Then, my AC stopped blowing cold air. I checked and the AC compressor is not cycling. Also, there is a tapping noise coming from the area around the evaporator. It doesn't sound like a lifter or an exhaust leak. It's kind of a high pitched tapping. Anyone have any ideas on what to check tommorrow when I have light? If it's just low refrigerant, I can refill it with a kit from an auto parts store right? How do I measure the pressure? I have switched to R134A a couple of years ago. It's just starting to get hot in Texas, so I need to get it fixed as soon as possible.

------------------
82 Camaro:
350
Erson cam, ported heads,Comp Cams 1.6:1 rocker arms
Edelbrock Performer RPM intake, Holley 600
Crane Hi-6 ignition, Accel supercoil
TH350 tranny with 2500 stall.
Eibach Pro Kit
SLP 1 3/4" headers