A/C Puzzle

I've been trying to fix my AC problem in my 2001 l series. Started out with the dealer saying I needed a new Compressor.I replaced the compressor and clutch and it would still not come on. Did some tests and found that the comp wires were shorted.What could cause this problem? By the way I also replaced the receiver dryer and the expansion valve.checked the ac diode and it is bad.Could this be the problem?