It appears that you are you saying that a direct connection of the hot wire to the blower motor results in the blower motor spinning. Probably spinning at a high speed with the direct connection? If yes, then the first thing that I would check is the resistor module with an ohm meter. If the connection is open and not showing a measurable resistance, then I recommend replacing the resistor module. Rock Auto has replacement resistor modules as a reasonable price.
Knowing your year, make, and model/trim of your truck will make it easier for other folks to chime in more accurately with their suggestions.