# Furnace Noise during startup



## hedgehog88 (Nov 3, 2013)

Hello,

I have a couple questions regarding a furnace noise I'm hearing during its start-up. I notice this noise has gotten louder than what it was a month ago, loud enough to make a rumbling sound which could be heard on the main floor. After self assessing the furnace I found out the rumbling noise is coming from the black disc like motor cover in the first photo. My initial thoughts was that it required manual oiling but doesn't look like there are any oil pin holes, at least not similar to the ones from oiling photos/videos I've viewed online. I don't know if anyone have experience this issue, but if you have and can help explain to me what the problem may be that would be greatly appreciated.

Another question I have is more out of curiosity. In the second photo there is a round opening which is attached to the air intake, I believe that is its name. As the opening isn't connecting to anything, does it have to be closed up or should it be opened for, my assumption, additional fresh air intake?

Thank you.


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## kok328 (Nov 3, 2013)

The black motor your hearing is the inducer motor.  They don't last forever and the bearings could be going bad.  Mine makes an awful noise too but, has been running like that for 6 years now.
I can't say for sure if the open duct is supply or return air but, if it were me, I cap it off if no apparent reason for having it open.


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## hedgehog88 (Nov 3, 2013)

kok328 said:


> The black motor your hearing is the inducer motor.  They don't last forever and the bearings could be going bad.  Mine makes an awful noise too but, has been running like that for 6 years now.
> I can't say for sure if the open duct is supply or return air but, if it were me, I cap it off if no apparent reason for having it open.



Thank you for the reply, kok328. There is actually 2 motors in this unit, the black motor and another one at the bottom facing to the side. Correct me if I'm wrong but isn't the inducer motor that blows the air through the furnace? If that is so, then it would be the bottom motor. If that is the case, what exactly is the black motor then? From looking at it over again,it looks like its carries something else through a white pipe sticking from the left side.

For the opening, I would agree also, just wanted another opinion. Thank you.


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## nealtw (Nov 3, 2013)

The hole in the duct looks a little DIY with the duct tape that should never be used on ducts. Someone did a bunch of work for some reason, perhaps there wasn't enough return air from the basement.


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## kok328 (Nov 4, 2013)

Possilby the old opening for a humidifier?  Cap it off.


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## hedgehog88 (Nov 4, 2013)

Hole capped, thank you.

As for the black motor, anyone have any idea what it does? If I got a closer shot would it help? I don't know if I can oil something like this to stop the noise.


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## Blue Jay (Nov 4, 2013)

The inducer motor is for combustion air, the one at the bottom is what moves the air through the furnace into the living area.


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## bud16415 (Nov 5, 2013)

Looks like someone could have had a wood stove next to that duct and perhaps they had some homemade method to divert heat into the system thru that point. Good you closed it off. 

Looks like the motor is an easy change out when the time comes. I would probably remove it and see if I could see anything to clean or oil and to know what is involved in changing it. Get a price and availability on a new unit and then make up your mind if you can live with it for 6 years or so.


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## hedgehog88 (Nov 6, 2013)

Blue Jay said:


> The inducer motor is for combustion air, the one at the bottom is what moves the air through the furnace into the living area.



What is the bottom motor fan called, out of curiosity?



bud16415 said:


> Looks like someone could have had a wood stove next to that duct and perhaps they had some homemade method to divert heat into the system thru that point. Good you closed it off.
> 
> Looks like the motor is an easy change out when the time comes. I would probably remove it and see if I could see anything to clean or oil and to know what is involved in changing it. Get a price and availability on a new unit and then make up your mind if you can live with it for 6 years or so.



I'll have to look and see if its a DYI thing. I would imagine I'd have to go back to the manufacturer to get a replacement if need be, correct? Its not like a general part which you can replace with another 3rd party, I assume?

In any case, thank you guys for your assistance.


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## kok328 (Nov 6, 2013)

The bottom motor fan is called the blower motor.
If you mechanically inclined and have access to old parts, you might be able to retrofit a Fasco motor from some other application to install into the furnace, otherwise, you will have a hard time trying to get your hands on this motor without having a mechanical license.  If you know somebody who does HVAC work, they might be able to order it for you.


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## ozone (Nov 6, 2013)

Many HVAC parts are available from Amazon.  I know they sell FASCO inducers as well as showing cross-references for proper application.  Reading the customer reviews might also give the OP a better idea if replacement is something he is comfortable with.


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## nealtw (Nov 12, 2013)

Looks like ???
http://www.buyfurnaceparts.com/aire...f90mpb-inducer-motor-assembly-exhaust-blower/


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## hedgehog88 (Nov 13, 2013)

nealtw said:


> Looks like ???
> http://www.buyfurnaceparts.com/aire...f90mpb-inducer-motor-assembly-exhaust-blower/



Definitely looks like that.  Nice find! However, I am going to stick with what I have for the time being. The furnace unit overall is old so if it goes I will likely replace the entire unit. I wish I had the manual for it. Would like to know if its possible to oil such a motor. :S


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## nealtw (Nov 13, 2013)

It did look like like a lot of money, you might find a local motor shop and ask them if they might be able to change the bearings. I have a rewind shop near me and they have fixed some junk for me.


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## bud16415 (Nov 14, 2013)

Many furnace repair guys save motors and stuff they think might be useful when changing out a furnace. My motor died on a Sunday a few years ago in a blizzard and I called around and no one would sell a motor just come out and replace mine in a few days. I called one guy and he said he had a garage full of parts and if I could get in his place he would sell me one. I got there and he had a 500 ft drive with 3 feet of snow in it. So I dropped my blade and cut a slot back to his shop. He had two motors like I needed and I asked how much for both and he said they are yours if I made a couple more passes at his driveway. Worked out good for me and him and I have a spare now.


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## nealtw (Nov 24, 2013)

SpecialtyAirInc; This is a self help site, I am sure if people don't get usable answers they do turn to the pros but as long as this is your specialty, some advice might be usable.


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