You won't believe the sound my furnace is making! Please help

[bobsmiley]

here's a video link that shows my problem pretty clearly.

https://www.youtube.com/watch?v=zUmJMXC2RaM

The furnace is an Amana 80 SSE. Any help would be appreciated. I actually threw in the towel on this one (furnaces aren't my thing) and hired an outside guy to come look at it...but he said the furnace looked good to him. At the time it appeared to be operating normally.

I have a couple young kids sleeping in the house with my wife downstairs, is this something I should send them away for? Is it dangerous?

[Cinder]

I watched your video, and saw this on the sidebar.

https://www.youtube.com/watch?v=zaT-gcEYpvs

At 7:10..

A noisy furnace is often the result of the draft inducer motor wearing out.   If the circulation blower fan is causing the noise, The set screw on the blower wheel may have loosened, causing the wheel to wobble on the motor shaft.  You can fix this problem by tightening or replacing the screw or replacing the blower wheel altogether. 

[bobsmiley]

thanks Cinder,

is that the bottom blower? It looks like I need to tighten a nut?

[Greg]

Yep... if tightening the nut doesn't help, you'll probably have to replace the blower.  The upper fan is an exhaust fan that only runs if the burner is working.  The capacitor "going bad" could be a symptom of a failing blower fan motor. 

If it were me I'd remove the lower fan motor, and see if it just needs new brushes or something simple like that.  This would also allow you to see if anything else is loose or wrong on it.

[bobsmiley]

    thanks Greg,

    how would I buy one and what do I do in the meantime? Just stock up on electric heaters? I did a quick google search and this is what I found -

https://www.google.com/search?q=draft+inducer+motor+furnace&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a#q=draft+inducer+motor+furnace&rls=org.mozilla:en-US:official&tbm=shop

    How do I know which one is the right one?

I watched a youtube tutorial on how to take it out and it looked pretty easy to mess up.

[gmp029]

The noise starts right when you turn the furnace on, which seems to indicate the combustion blower motor (small top blower), since the main blower on the bottom doesn't kick in until after the furnace warms up.

Also Google search your furnace model and get the owners manual, it will tell you what the four flashes on the circuit board mean. You need to search the actual model # on the nameplate of the furnace, not just Amana 80 SSE.

Also make sure you have a working CO detector in your house!

[bobsmiley]

okay I replaced the capacitator and it's still doing the same stuff. Moving on to the blower motor. I don't think it's the top blower, just a hunch.

what are the new brushes you're talking about? Not sure what that means.

[Greg]

In your video, it's pretty obvious the upper motor is relatively quiet while the bottom one is making quite a racket.  So I would go after the lower motor.  Some motors have carbon "brushes" that rub against the armature and wear over time.  Many modern motors don't have brushes, but if yours does it could be one of the things that it needs.  The noise though makes me thing the bearings/bushings are bad.  If it's a bushing, you can sometimes get more life out of it with some oil.  If it's a bearing motor, then the bearings would have to be pressed off/on and it's pretty involved.

Once you remove the motor, you can inspect it for bad bearings, loose parts, etc.  Also, you can google the part number on it and see what your options are for replacement.  You may even be able to take it to a furnace company to see if they have a replacement.  If so, you could have it back together in a day.  Otherwise you could be in for a wait in which case some space heaters are a good idea.  Just be careful in how you use them.

[bobsmiley]

okay the lower blower has been replaced. It's much quieter now, but the furnace now doesn't turn on at all. I'm wondering if I did the wiring wrong when putting it back together, but it looks right to me (took pictures before hand)

Now when I turn it on, the high limit switch error happens immediately and I don't get a flame at all. I'm thinking faulty high limit switch? Or loose wiring? Not sure.  It seems to me that it can't be overheating though because it's been off for quite awhile (a few hours) and it flashes soon as it is turned on.

[bobsmiley]

still no heat. I'm afraid I might have to get a service tech out here at this point, the house is reaching 45 degrees now. I don't want to deal with frozen pipes. I called and asked what it would cost to replace a open high limit and it will be around $200. There's no one around here that sells one.

If anyone has any other ideas let me know...I don't know what else it could be.

[bobsmiley]

okay I did a reading on the high limit and the round disk (not sure what it is)

the high limit registered a resistance I think? The number was bouncing all over the place though.

The round disk showed no reading at all.

[bobsmiley]

  the high limit is stuck open, I ordered a replacement. I think the only thing left is to get the limit out of the furnace. It's behind the gas line(?) in mine, and I will have to take the whole thing out just to get the limit out. No clue how to do that yet. Still searching

[Greg]

I'm afraid you've surpassed my knowledge of these things... good luck!

[nordlead]

Too bad I didn't see this thread when you first posted it. I had my blower motor fail just 6 months ago (in the middle of a +95F heat wave) and sounded exactly like that. It also gave off that familiar burning electronics smell as the motor overheated. The reason you got all that noise is probably because the bearing went bad causing too much resistance for the motor to get up to speed. While you can easily spin it by hand, it isn't nearly as free as a good bearing. Mine would eventually get up to speed and the noise would go away (for a while until it completely failed). Some blower motors have bearings you can oil, others are sealed. Mine was a sealed bearing so the blower motor had to be replaced (theoretically you could replace the bearings, but that would have been too much work compared to a $125 replacement motor especially as I don't know how much other damage the motor suffered). If you can oil the bearings you should see two (possibly yellow) caps on the top side of the motor (one for each bearing). Just something to check out and keep in mind for future maintenance as obviously you already replaced it.

As for the over temp sensor. Did you try shorting it? If it is stuck open (assuming it purely switches open/closed) causing the furnace to turn off all the time, then shorting it should give you heat to prevent your pipes from freezing. Obviously it should be replaced ASAP. I would probably just have someone monitor the furnace while it is on and only run it long enough to keep the pipes from freezing. We did this on a dryer that had a bad temperature sensor until the part came in, but at least with that you are running it for only ~1hr and you can easily keep an eye on it.