I dont know the exact voltage relationships but, the small wires to the blower regulator are low voltage control from the fan switch. Should range from 1 to 5 volts, or 3 to 9. The output is from 6 to battery voltage. Whats the amperage draw of the motor? It should be around 20 wide open, more than that and your pushing your luck with regulator and fuse.
Hope this helps,
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.