a/c hasnt the right power

[brakecheck]

so here is the problem.... both wires are the a/c compressor are ground also at the lo/hi switches. I have checked all fuses and they are good. I have also checked the wot relay. one post is positive while all the others are ground. i have been looking and have torn the wiring harness apart looking for a short to ground and cant find any place where the wires are worn or frayed/melted. i have also looked to see if there is anyplace where wires could have wielded there selves together. I can find any place where that could be. I know there is the right amount of freon in the system. I have captured all the old freon, vacuumed it down and placed the right amount of freon back into the system. i did hot wire the compressor to the battery and it works that way. I have also used my scanner to check for codes and there are none. I have also used the scanner to run tests on the climate module and it passed. the scanner is a snap on 5k what ever it is. I understand it cant do everything that the ford scanner will do. I'm really at a loss here, anyone that can point me in a direction or may know what it causing this to happen I would really like some imput. also when I say ground I do mean negative. also i have used a multi meter and the negative voltage is at 13-13.5v. thanks in advance.