Blower motor is making humming noise

[ejl7]

Hey guys. My blower motor was making a whining noise that would start at about the fourth bar and wouldn't go away unless I turned the fan all the way up or dial it down just below the fourth bar. I was advised to replace the blower motor. I did, with a brand new one OEM. It worked great for a about ten days until it started back up. Not as loud as before but it worked it's way up there again. I don't know what to do. I was advised again by the same mechanic to make sure that the housing was clean, for the smallest amount of dirt could be causing the noise. I have inspected the housing and find it to be solid and clean. What gives? Could the resistor that controls the speed may be wearing out?

Help!!!!!

[protech5]

No but did you replace it with new?

[ejl7]

No, the resistor has not been replaced. All speed settings and increments in air flow are normal. I was advised that perhaps I should take it apart again and inspect the housing. Perhaps the rubber lip of the upper cover attached to the housing is a little loose, therefore responsible for that hum. I will try to take it apart tomorrow, I'll let you guys know. Thank you sir. Perhaps I shouldn't have replaced the motor, the rpms were still good though since the brushes were worn down to about 40% I'm glad I did.

[ejl7]

I guess that I cannot really fix the problem. I took the motor out again and inspected everything. Casing is clean, pathways are clear. Motor is brand new though the humming noise is still there. However, I do remember when the flaps failed sometime a year and a half ago and I got a classic error code 8 that the humming started around that same time. Perhaps when the flaps broke, a little piece of plastic must have lodged there. eventually I got my flaps fixed with the replacement stop arm, though I'm afraid that unless the whole core is pulled out and inspected, we will never know for sure. I'm afraid i'll have to live with it.