I'm not sure if this will help in your case but I wrote up a fan repair tip that may apply to you.
This is a tip for rejuvenating computer “Boxer” type fans that squeal or speed up and down due to bearing wear. These are some basic guidelines. In order for this to work you need to be able to access the rear bearing of whatever fan you are trying to work on in case you are working on a blower type fan. If you CAN’T find a way to get at the bearing it won’t work.
What you will need:
Buy some graphite powder and some 3 in 1 type light lubricating oil at hardware or at an automotive type store. You can usually find graphite powder in a stores house key dept. If you can find it the best option is a pen-type needle tipped sewing machine oil dispenser as they are easy to handle and only give a small amount at a time. If you CAN’T find a pen type dispenser you can put a drop of oil on a piece of aluminum foil and use a toothpick to dab and transfer a small amount of the oil to the fans bearing. DO NOT DAB WITH A COTTON SWAB! It will leave fibers that will wrap around, bind the bearing and be VERY MESSY. The graphite powder comes in small plastic tubes. You have to “Puff” it from the tube so take care its very sensitive. MAKE SURE you get graphite POWDER, not graphite oil because it’s too thin for this.
Step #1 Use a tiny Jewelers screwdriver or a sharp knife and carefully peel ONE edge of the center label covering the fan bearing in the middle of the fan.
Step# 2 Remove the small rubber plug covering the fan bearing (if there is one).
Step #3 Once you have exposed the brass bearing put a VERY small amount of oil on the bearing FIRST and then add (or puff) some graphite powder in the same place where you just put the oil, You are only going to put a drop or two of oil and powder. Don’t smother the bearing.
Step #4 Clean off excess oil and graphite and push the label back where it was. You may need a small amount of duct tape to hold the label in position and to prevent leakage. This is important if the fan is going to "sit up" as opposed to lying flat.
FYI- The reason you put the oil on the bearing first is that it will draw the graphite into the bearing as it spins. DO NOT USE WD40 or any lubricant that has an aerosol type solvent in it since it will dry out shortly and you will be back in the same boat. The graphite powder is very MESSY so make sure you don’t spill the powder all over the place when you puff it on to the bearing.
Hope this Helps - Bohanna