A Question for Small Motor Experts

Hi all, I just received a replacement cooling fan motor from SNG. I am going to use it on my 63 FHC restoration, which will have a positive ground arrangement. There are no markings on the spade terminals to the motor. Concerned as to how to hook it up, I applied 12V power to it in both a positive ground and a negative ground fashion. Both arrangements caused the motor to rotate clockwise, when looking towards the output shaft of the motor. So I guess I can’t hook it up wrong! My question is why does the motor rotate the same direction no matter the polarity of the hook up? I’m guessing the magnetism of the field winding must “lead” in such a way that it always pulls the armature in the same direction. Am I close in my thinking?

BTW I attached my fan and it does blow air to the rear.

A Permanent Magnet motor will switch directions when the polarity is switched, because the magnetic polarity of the field is fixed. If the motor uses a coil to generate the field magnetism then the polarity of the armature and the field will both switch when you switch the electrical polarity. That means their polarities are the same no matter which way the current flows so the motor will turn the same way. For a more detailed explanation look up “DC Motor” on Wikipedia.


Thanks Mike!!!