The blower motor in my car suddenly decided to die on me. There is voltage going to one pin (0 to 12V depending on the fan setting), and continuity to the ground, so I know the logicon and relays are working as they should.

So, I turned my attention to the motor. I took it apart and cleaned all the crap out of it, but that hasn't helped. So then I lightly sanded the brushes and the commutator contacts and confirmed continuity from the electrical contacts to the tips of the brushes. All good. I am also seeing continuity from and to all commutator contacts, but I can't remember if that is correct or not. Other than that, I'm stumped. What am I missing?

 

NEVER EVER sand brushes or comms. They wear into each other, and if you change that, you need to go through the break in proceedure again. Not a big deal with this tiny little motor that is already inefficient, but it's a general rule.

Have you applied 12V directly to the blower motor to test it?

 

There was plenty of material left on the brushes, so I wasn't too concerned about that. They'd probably re-seat within 5 minutes.

Nope, haven't tried power directly to the motor yet. Was going to, but it was getting late and I thought I'd call it a night. Will do that tonight though.