I’m restoring my 77 k10 and have installed a new wiring harness. Also bought a new heat/A/C fan switch. My blower motor comes on when the ignition is turned on, which is normal. I have 3 fan speeds that work perfectly but when I put the fan to high, I blow the fuse in the fuse panel marked heat/AC. If I unplug the relay (which is new) the fuse doesn’t blow. Of course the fan doesn’t come on either. I have ohmed the orange wire back to the switch and it is ok. I’ve also put voltage on the orange wire to make sure it wasn’t grounded out somewhere. I do have ignition voltage on the red wire coming to the relay. The blower motor works fine if I connect it straight to the battery, which is high speed. I’m going to test the relay this weekend to see if I hear the switch operating. I don’t think the high speed goes through the resistor, but I did take it out and it looks fine. Am I missing another spot that I need to check? Could the new relay be shorted out causing the problem? Any suggestions would be greatly appreciated!