Strange blower motor problem

[SmokeyBear]

First specifics: 72 F100 Ranger XLT, Factory AC

Problem - Blower motor not running.

What I've checked - I've tested the motor by running 12 volts straight from the battery to the orange wire to the blower motor. MOTOR WORKS.
I've checked power from the switch to the resistor. The plug that goes into the resistor has power at one of the prongs when switched at the control switch which means the switch is working and the power is getting to the resistor. With the plug connected to the resistor, there is power at the prong that goes to the blower motor (where the orange wire connects) 12 volts when the orange wire is NOT connected. when I do connect the orange wire to the prong there shows NO power. I'm thinking it is the resistor but there seems to be no damage to the coiled wires or anything else on the resistor. I'm stumped at this point, can anyone help? Thanks in advance.

[Ranchero50]

Check for voltage with the motor in the circuit. At times there will be resistance in the switches. Old theory, open below the reading point will show full voltage, open above will show nothing.

[Bronco_77]

Check all ur wires and make sure the copper doesn't have a black tint to it if it does it won't carry voltage right. It will show proper voltage till its under load I had to rewire a backhoe over it once and a off road desiel feul tank last Saturday over it.

[SmokeyBear]

One problem fixed, now another. I found a wire that the PO must have added. The light for the AC controls were wired to the brown wire that feeds power to the HVAC system. As soon as I clipped it, the blower started working. I let it run for a few minutes while I hooked up the gauges to see if there was any pressure in the system and it blew the fuse. I replaced it and a few moments later it blew again. The fuse was HOT. I THINK the prongs that hold on to the ends of the barrel fuse is very loose causing it to heat up. I'll try to sand them down and bend them to give a better grip on the fuse and report back.