a/c screeching

I've just installed a vintage air system on my street rod. I bought the compressor about 4 years ago while modifying brackets to install. Finally got around to charging the system, but when I engage the compressor (Sanden) on the control panel I have a loud screeching noise. I have a serpentine belt running all accessories. When I engage the compressor the belt seems to stop and not turning around compressor pulley. I sprayed the front of the compressor clutch with WD 40 which helps noise for about 30 min. but it reappears. System is cooling. Compressor cycles off/on, but screeching starts again when WD 40 wears off. Could the compressor be bad? Any help is very appreciated!

Three things come to mind:
Bad Compressor
Insufficent belt contract with the compressor pulley
Overchargered system

what kind of cooling fan do you have? if you have a elec. fans it needs to come on as soon as you cut your ac on, or the head pressure will go to high and lock up the compressor. you have got to have air coming across the cond. at all times. have you got gauges hooked up ? if so what are the readings?

I agree with both of yall, bad comp or high head pressure.

By the way welcome to CHR.

yup to all responses above.

Thanks for all your help. It looks like the problem was that my compressor had been on the car for about three years without being connected and without the a/c charged. I think the clutch must have had a little rust from being unegaged for so long. I soaked it overnight in WD 40 and put about a 100 miles on the car with NO squeaks at all. Thanks again for your response.