On Tue, 5 Mar 2019 17:35:08 -0800 (PST), wrote:

I have a similar problem. When the furnace shuts off, I've been getting a squeak. I took the access cover off, and don't get the squeak when the cover is off. When I put the cover back on, it squeaks.

I'm thinking I may not be getting adequate combustion air and there's a sudden change in air pressure in the furnace when the burners/fan turn off.

I tried putting some silicone spray lube on the rubber gaskets on the access panel, but that hasn't solved it.

I'm not sure how to go about checking the combustion air supply.

Thanks.
Pull the eductor fan and look at there the squirrel cage is joined to
the hub. When mine did that I found a fine dusting of rust -
indicating the joint was loose and "fretting"
New fan was not in stock, was several hundred dollars, and no
guarantee the costr would be covered so I just brazed it and it hasn't
squeaked since - mine squeakes starting and shutting down.