[dfgtre76]

I've noticed after my furnace shuts down the fan blower has been making a sound as the fan slowly comes to a stop. On every rotation it will make a soft "boom" sound. There isnt a screeching sound like the fan blade is grinding against metal, its just a subtle boom on every rotation. I opened the unit up and manually spun the fan blade myself and the sound is there.


Im afraid the alignment or something is slightly off, could it be the set screw? I tried turning it with my hand and it seemed tightened.

 

[Windows on Wash]

What is the "boom" sound when you manually spin it? You sure all the bolts are tight and there is nothing else loose? How are the blades themselves? Sometimes, the squirrel cages come apart.

 

[dfgtre76]

The best way i can try to describe it is every time the fan blade makes one complete rotation there is a knock (knock probably describes it better than a boom).


Nothing is loose as far as i can see, nothing is grinding, it spins smoothly (besides the one knock), the blades appear all intact and undamaged.

 

[roughneck]

Could be coming from metal ductwork as the static pressure bleeds off.