You can tell it's summer by the number of A/C questions. Here's mine. Reputable service guy says I have a full charge, no leaks, compressors is fine on my R-12 system. He said it worked fine, after fixing the ground connection from the compressor. But when I turn the little rotary nob to the max position (or any other) all I get is a little (5 degrees F) temperature drop at the output and nothing more. I once had it really cool off for about 30 minutes then it quit cooling. The fan runs fine and the compressor clutch engages with a corresponding increase in engine speed. Fuse is new and in good shape. What's the deal? A/C relay, expansion valve, heat from somewhere, damper failure?

Thanks in advance.

Tom