squealing furnace

[Donnie2003]

Hi, again--another question to a problem that's been plaguing me for a while ...

Squealing, squeaking noise coming out of furnace blower. I've periodically oiled the blower motor bearings, changed and adjusted the belt, and still the irritating noise persists.

I was wondering if it was due to a leak in the ducts, when I discovered a mystery vent coming out of the back (please see my other thread about that).

Any ideas how to fix?

Thanks again! -)

[Donnie2003]

Just wondering why my posts have random asterisks popping up instead of words now and again?

[Donnie2003]

again

[Freon]

Squealing is usually a belt issue, assuming you do not have a direct drive blower wheel. Belts are inexpensive at most auto stores. If the belt hasn't been replaced in a while, start there. You can also grab the blower wheel and see if there's play at the bearings. Move it up and down, right and left. With the belt off, spin it. If there is no play and it spins freely and quietly, your oil maintenance is working. Go for the belt.

[Donnie2003]

Thank you for your quick reply, Freon!

No, it's not a direct drive ... I changed the belt recently and it was okay for a while. If the furnace has been off for a time, as after the summer, or even after turning it really low for a half-day or so, it won't make that noise for weeks, sometimes over a month. Then, all of a sudden, it will start doing it again. That's when I turn the heating off for several hours and give it a rest again. I usually oil the motor bearings or check the belt and see if it's too tight or loose. I had the furnace off for several hours after I posted and now it's back on again and not squeaking.

I was wondering if perhaps something like this could happen if the air in the basement gets too hot and dry that it brings on the squeaking noise in the wheel or dries up the oil in the bearing. In my other thread I mentioned how there was an extra hot air duct opening down the back of the furnace unit. The basement is easily the hottest room in the whole house because of it. (please see other thread)

But I will see how long it goes for this time without making noise. Then I will change the belt again and maybe clean any dirt or grease from the grooves in the wheels. (Or try to, the unit doesn't conveniently open from the side to allow access to the back wheel and blower. It opens from the front and there is no way to get to the side because the water heater is there).

[Freon]

All atmospheric changes in the basement will affect the fan belt you're using. In cars we have tensioners that keep a constant pressure on an idler pulley so the belt tension stays constant no matter the humidity or temperature. Usually in a furnace we don't have those tensioners so you have to do it by hand. Be sure the belt pitch is the right one for the blower wheel pulley and motor pulley. The manufacturer should have the exact part number for the belt you need.

If the bearings were going I'd expect a constant squeal, not intermittent like you have, which, as you have noticed, seems dependent on atmospheric conditions.

[Donnie2003]

Thanks for all your help, Freon! I'll be sure to return to these boards if I ever have any problems in the future. -)