Power at the red wire simply means you have 12v feed from the fuse box.
The regulator is in the ground line for the blower [ switched ground] and it is triggered by a variable voltage from the yellow wire coming from the PB unit.
Look for 2-8 volts at the yellow wire with the PB unit ON. If you have that, then the reg is not tripping.
In that case , the blue wire coming from the neg side of the blower motor
to the regulator can be jumpered to ground. If the motor then works , you have a bad regulator.
Just make sure you have trigger volts at the yellow before diagnosing the reg. as bad....