The blower is making a horrible noise -- sounds like bearings to me, but on the net I saw mention of possibly some water? This is the induced draft assembly, not the big squirrel cage at the bottom. The blower is right in front of the firebox.
Depends if you have a 80 percent or 90 percent furnace as to the draft inducer seeing condensate or not. If you dont hear a 'swishing of water sound' then you can rule that out. If the sound is a high pitched sort, then it does appear the bearings are failing....although I found a small dead bird in a draft inducer assembly which created a higher pitched whine. Shut off the power to the furnace then turn the inducer fan by hand/small screwdriver ....and see if you can duplicate the sound with the power off. Its more than likely bad bearings which requires replacedment of the entire draft inducer assembly : $$$
I would have sworn my draft blower bearings were bad on my furnace so I took it off to check and the bearings were PERFECT. The chirp was still there, so I looked more deeply into it - and noticed a bit of red "rust" around the hub of the blower squirrel cage. The disk of the blower was just a bit loose in the hub - the crimp was bad. I hit it with a bit of brass and the acetelene torch and no more chirp.
Just goes to show you sometimes need to look for the unlikely.
I've replaced several of those. You can call a heating company. Or, if you're a do it yourselfer, you may be able to replace it yourself.
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