1981 Silverado, 193K + miles, 350 motor, 2wd. The fuse for the blower motor blows each time the speed is switched to Hi, it works in the other positions(speeds) with no problems. I have replaced the blower motor, the fan switch and the blower motor resistor. I have also made sire the plug for the switch is not melted. Is there anything else to check? Thanks for your help.