I think the contacts are fine: I can distinctly hear the compressor clutch engage and load the engine when on AC or Max AC setting. I think this is pointing to the resistor QK mentioned?
Look at the diagram. This is in the AC section of the "heaters and AC" chapter 24.
The compressor and blower are serviced by SEPARATE fuses, and the power for the blower and compressor come off SEPARATE switch contacts
Here's the diagram out of the '73 manual, which is the same as the 74 shop manual
High speed blower has nothing at all to do with the resistor, unless it's a bad connection at the connector where the two wires junction. You could unplug the resistor and toss it in the garbage, and the blower would still turn fine in high speed
Black dots are the compressor clutch, yellow dots are the blower power