I have a problem with my a/c and need suggestions on how to fix. My compressor clutch keeps engaging and disengaging. It clicks on for 2-3 seconds and then clicks off again. I was thinking it might be low on R-12 but I remember seeing a thread somewhere about a relay or pressure switch. When you drive it the air blows cool but with the heat of the afternoon sun it just can't cool the car. Anyone have this problem and how did you fix it?

you really need to hook your car up to a set of AC pressure gauges so you can see exactly whats going on. Too tough to guess, but those gauges will pinpoint the problem.

If you're low on refrigerant, what happens is that if you were to hook up pressure gauges, you would see it shoot down to the low pressure cycling switch setting (aprox 26 psi) and then slowly rise to 45psi'ish. At that point the compressor would turn on again and it would drop like a rock to 26 again.

If you have too much refrigerant in the system (overcharged) it would never get low enough psi to cool. Compressor would never shut off. Not good for the system and won't cool cold enough.

So the car as is (undercharged) will go down to the low psi, low temperature. But it won't run long enough before cycling off the compressor. Your compressor will probably cycle on/off/on/off less if you turn the fan speed up. It won't fix the problem. But it's a temporary band aid until you can get the leak fixed and some refrigerant.

after hooking up the gauges it is apparent that I am low on R-12. After searching for a shop with some r12 to no avail I decided to just convert the system over to 134. It now blows cold. I hope this is not a short term fix.