I had the squeaking last week, now no motor at all.
This happened a couple of years ago and I did all the testing , grounding some lead and the blower motored was fine. I ended up replacing the regulator.

Could it be the motor stops freezes up and then blows with regulator. I will do the test again today to see if is the motor or the regulator.

Either way I have very little heat coming for the cold weather predicted this week.

Mike Sheehan
1992 300D -- 218K