OK do both doors have a sight hole? Or just 1? The vent motor should be in the one with the gas valve. Is that where the loud humming is coming from?

Yes, I think the humming is coming from the same area as the gas valve.

OK there should be a switch down there that turns off the power to the unit. Shut it off. Then you will need to take off the panel where the gas valve is and locate the vent motor.

Yes, there is a shutoff switch right there. I can do that... But, what do I do after taking off the cover? Sorry, but its difficult for me to crawl under the house... just trying to save an extra trip up to check the computer.

OK find the vent motor, touch the back of it and see if it is real hot. Then turn the power switch back on and make sure it is the motor that is humming. Then turn the power back of and let me know what you have found. Take your time

If it is the vent motor that is humming and is hot. Either the motor on it is going bad and they are quit costy for a new on or something is stuck in it like a bird or twig. Birds are building nest all over this time of year. There is 3 bolds that hold the motor on you can remove them and the power plug take the ventor outside where you can see it and see if anything is in it or if the fan blade will spin

OK... vent motor is the problem.

I was wrong about the gas valve, what I was looking at was the vent motor. Once I got the cover off, I could see that the noise was coming from the fan.

OK, so I moved the fan blade... it seemed "stuck" at first, but after I moved it, everything seemed OK. Then, when I turned the switch back on, nothing happened.

So, I came up here to report and heard the fan on, then the burner on, then the heat blower fan... everything normal.

I am concerned, though, about the vent fan being "stuck"... maybe its time for a replacement? Looks like a pretty easy job... now that I know I can easily get to it.

THANK YOU for your help, BTW!! I'm glad you were willing to help a stranger...

Thanks, again!

Great glad I could help, sometimes after you free them they will run for a few more yrs, sometime a few more days. I would probably get one before next winter. But as you was saying spring is almost here and that part is going to probably cost around $350 or so. Good luck. Have a great weekend

WOW! $350 for a fan motor sounds pretty high... I'll see if I can free this one up some more... maybe its rubbing on the housing or needs a bit of lubrication.

There is a remote possibility that something foreign got in there. Taking it out should reveal anything out of place.

Again, thanks for your help!