Furnace noise

[ksg5000]

Furnace has gotten louder - hard to describe but like something is loose and vibrating when fan motor is running. I took the outside cover off and didn't' see anything obvious - the fan doesn't appear to be hitting anything and moves fine by hand - screws/bolts appear to be tight. Any thoughts? Thanks. Kevin

[D_E_Bishop]

Our fan was getting noise and did sound like excessive compression noise. Ours had bushings and it is really not lubable, besides it is a pain to get to. Suddenly the compression noise change to a squeal, a very loud squeal, a banshee loud squeal, at 2:00am in the Black Hills with an outdoor temp of 19 degrees. We're from So Cal and had no backup heater. Now we have a new motor and it no longer wakes me up. A motor with bearings instead of bushings and a very clean squirrel cage fan. So yes a motor with dry or bad bushings can make some funny noises.

[joshuajim]

ksg5000 wrote:
Thanks for the comments - I have checked the squirrel cage it turns fine and I can find no obstruction.

In reviewing furnace noise threads I had come to the conclusion that worn bushing/bearings result in squealing noise not the kind of noise I am hearing. Would/could a worn bearing create a "non squealing" noise?

Are you aware that there are 2 fans. One to circulate the heated air and one to purge the combustion chamber. Have you checked both?

Typically you have to remove the motor to check the second one.

[tpi]

My latest Suburban furnace the fan/ motor is slightly out of balance. I can definitely feel it in the furnace when it is running. It has not proven to be noisy (yet). Given the speed and small amount of rotating mass, I can safely conclude they didn't shoot for the moon on the quality of the fan and motor.

If the fan/motor is exciting rattles and noises, I'd check the root cause: balance. I don't know if these can easily be balanced, or a replacement is in order. Anything you could do to cut down on vibration would be beneficial.

[ksg5000]

Thanks for the comments - I have checked the squirrel cage it turns fine and I can find no obstruction.

In reviewing furnace noise threads I had come to the conclusion that worn bushing/bearings result in squealing noise not the kind of noise I am hearing. Would/could a worn bearing create a "non squealing" noise?

[Dave_H_M]

It seems that you are checking all around in and out of the squirrel cage (assuming that furnace is built that way).

I had a mud dobber build a nest in one - what a surprise. Ever since then i have had a screen on the intake and exhaust ports.

[BobsYourUncle]

Maybe the bearing in the fan is going south.
Get in there and grab the fan and wiggle it to see if the shaft wobbles. It might have a bushing as opposed to a bearing - I don't know.

[cochise49]

Foreign object? Our furnace got very loud after a year of use. Couldn't sleep with it running. Techs found the installation instruction sheet had been left in the furnace/blower space by the factory. It had gotten lodged in the fan. Removed it and all was well.

[doxiemom11]

Ours has started that also, sounds like the fan is loose/wobbly until it gets going faster, then the noise stops like centrifical force corrects the wobble. We cannot find anything to tighten and all seems fine when checked. Another forum indicated that the fan motor may be going out when this happens. I guess eventually we will find out. Ours is in a 13 year old coach, not sure how much it was used the first 10 years, but we have used it quite a bit in the 3 years we have had it.

[ksg5000]

toolman1 wrote:
Maybe the plastic hose leading to the outlets has a tear in it, and is flapping?

Wasn't aware of a "plastic hose" - where can I find that? If you referring to the interior hoses which transport heat I made sure those are tight/OK and not contributing to noise.

[toolman1]

Maybe the plastic hose leading to the outlets has a tear in it, and is flapping?

[ksg5000]

Thanks but fan isn't dirty (cleaned anyway).

Anybody have other thoughts?

[RoyB]

Our propane furnace blower loud GRRRRR sounds like sitting in the last two seat rolls of a M80 jet airliner to us...

Wakes me up every time it kicks on...

With this in mind it has become our backup heater with a very low setting of around 40 degrees. We heat with 120VAC Oil Filled heaters and electric blankets when hooked to shore power. We are thinking of switching over to HYDRONIC heat using our 6-gal hot water heater as heat source and yank that loud puppy out of there.

Roy Ken

[Dick_B]

This is a wild guess and totally without merit but could the fan be dirty and possibly out of balance?