My cab fan and AC has no function. The fuses are good but I seem to have lost ground at my blower motor. I ran a jumper wire to another ground source and the blower started working but the dial wouldn't adjust the blower speed and the AC blue light switch didn't show to be working. I traced the hot and ground wire from the blower to an aluminum box under and behind the operators seat. The box is about 5"x5" with other wires plugged into it as well. What is this and could it be my problem?