Anyone know if voltage is applied across which pins makes the motor spin??

'nother pic

i don't know but if i had to guess.... fan speed has low, med and high. if i remember correctly.

one pin would be ground. test by using ohm meter. touch one lead to steel casing and test for no resistance on the 4 pins.

after finding the ground, that is your neg pin. attach neg power lead to that pin and listen for fan speed when applying positive energy to the other three pins. =-)

if something begins to cook, please read someone elses disclaimer so that i may be disclaimed also.

best of luck.

From what I understand in the electrical diagrams, there is only one pin that is supplied with 12 volts, the one with the red and white wire going to it. The other three white wires are simple ground wires of which two go through resistors to reduce speed.

So I guess you connect the + to the red wire pin and - to any other one.

Another option is to detaching the lower assembly from the housing by removing the two 8mm bolts and connect power directly to the motor leads which will be obvious.