I've got power at my AC compressor but it won't engage. Both wires that connect to the compressor have approx. 12 volts. Is this normal. It seems like one would have to be a ground. Any Ideas? AC was fine one day then I noticed it did not work. Found a blow 20 amp fuse in the fuse panel under the hood. I've also replaced the relay. Compressor/clutch haven't been making any funny noises at all so I'm thinking its something electrical.