Furnace Fan Noise

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Tom Hoffman

Tom Hoffman

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Once the burner turns off and shuts down and what would be causing a noise in the furnace fan after the furnace shuts down and the fan continues to run to dissipate the final heat we can now hear a noise like a bearing going out, can this be serviced?  is the blower going out?  We are in Yuma and the furnace is in nightly use and this is a new development.

Any help would be appreciated.
 
The fan is usually a squirrel cage and it's held on to the shaft of the blower motor by a set screw.

Sometimes those set screws loosen and the squirrel cage works it way towards one end or the other of the shaft and starts to rub on something causing the noise.

Simply loosen the setscrew, move the squirrel cage to where it clears everything and then tighten the screw.  Nothing to it, very simple.

Oh, you have to stand on your head and have three hands to get to it once you find the motor....mine is buried under my refrigerator. 

Great fun for sure.  What would we do for entertainment if we didn't have our RV to work on?
 
Thanks Arch, I kind of figured that's where it was buried,  I can't get down there with out a crane to get me back up, so it sounds like a job for SUPER wife. 

Tom...
 
Depends on the brand/type of furnace, actually.  My Atwood furnaces are setup so you can access the blower motor from the outside, seated comfortably on a bucket, with a cup of hot coffee(furnaces never fail when it's warm)provided by the loving wife. YMMV.
 
The motor "bearings" are actually bushings made of oilite bronze that are self lubricating,, but they wear out like any other part and can be repaired only by replacement.. Accessing and removal usually is a bear of a job, ( the Atwood being the easy one). My suggestion is to use the furnace model number and order the motor before you tear into it to minimize down time.>>>Dan
 
Ditto to the advice of the others. It might be one of the two squirrel cages rubbing and it's worth investigating, but if it's the motor I'd just replace it. They aren't horribly expensive.  There are two fans on one motor, one fan for combustion air and one for circulating heated air.

I had to replace one of the squirrel cages on an Atwood and it was a bear even though was accessible via the outer door panel.  I ended up pulling the furnace out to do it. Wasn't all that hard to get out. Mine was the 2-speed, dual btu, model, so a bit more crowded inside and dang near impossible to get the squirrel cage out with the unit in place.
 
Temps so darn low here in Yuma that I'll wait for warm up and then call a tech to do it.  Thanks all for your experience.

Tom...
 
Well when it is a noise "Like a bearing going out" that could be the problem

It could also be nothing more than a screw loose.

On one AC (plastic blower) the hub was cracked and it was making a terrible noise.  Late Friday. Hotter than hot.  and of course the nearest open parts store is far enough aay it won't be open when you get there..  So where was the RVer going to find a new or used in good condition blower????

My basement... I had one.. Still do.
 
We had the fan start making noise after hitting a speed bump; must have moved it out of alignment just enough to rub against something. Before I had a chance to take everything apart, we got bounced around on a rough section of road. After that the noise stopped.

That must have been six or seven years ago - the noise hasn't returned.
 
Not unusual for the sail switch to shift and rub the squirrel cage fan assembly.
 
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