It's an old trick, but, still works.
If your blower motor squeaks or sounds as if it's just all it can do to spin.
Remove it and drill a 1/8" hole in the nipple looking part of it. (center of the back side, where the end of the shaft is).
Add a couple drops of oil, spin it by hand, add a couple more drops.
Then, with it in your hand, connect it back to power and see if that cured it.
If so, seal the drilled hole with a dab of rtv silicone and re-install.

When/IF it acts up again, no need to remove. Just clear the silicone, re-oil, and re-seal.
Use something heavier than wd-40.

 

Redlinear= Good info. LPS-3 would be a better choice then WD-40.
Thank you.

 

Correct. Don't use wd-40 or anything thin like that. I've always used simple 3 in 1 houshold oil. (due to always having a little can of it handy. AND, most importantly: Those little cans have a litte nozzle that fits that 1/8" hole just right)