1991 240 wagon, fan was working fine, I replaced the old factory radio with an aftermarket one, took out the amp and ran the wiring harness that connects to the old amp connector down through the radio opening and connected to the amp connector, was a little tight but no wires were loose, long story short put it all back together, everything worked fine except when I turn the knob to make sure the fan was working, nothing, I checked the fuses, they were ok, took it apart and found there was no power going to the knob, wire are all connected, don't under stand why no power, thoughts!