AC Problem

Background: Three years and 14,000 miles ago my car got a complete new AC system for $1265. The compressor is an SD7H15 Sanden Model 8104, made in Japan, that takes R134a refrigerant and SP20 oil.

When I bought the car two years ago or so it already had the new system and the AC ran cool but not cold. It got worse and worse, so I added two cans of refrigerant one year ago. It ran cooler for a while then stopped running cool. The compressor clutch starting clicking on and off, on and off, but without ever actually running the compressor. So I went the year without running the compressor. A couple days ago, in hopes of locating a leak, I added a pound of dyed refregerant successfully, but wasn't able to get the system to accept any more than that. The compressor still just clicks once or twice, then not at all. It won't turn. A mechanic I checked with told me to apply 12 volts directly to the compressor clutch lead with the engine running, so I tried that. All I got was a loud horrendous screech which caused me to cut the electricity instantly. I touched the wire to the hot lead a couple more times for a split second with the same result. Then I quit, fearing for my nerves and the life of my brand new Japanese compressor.

Any suggestions? What's causing the screeching? I'm in need of some help. I want the system to work, and I don't want to destroy anything in the process. I need to make the system work so I can load it with refrigerant and have it black-lighted to find any leaks.
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Thanks everyone for all the help, Doug C. 81 242 Brick Off Blocks, turbo bars and wheels, M46; 86 244, B230, 150k , auto; 81 242 Turbo, intercooled, M46, 122k.