# High-pitched sound from the furnace



## bobelectric (Mar 3, 2007)

Sight unseen, oil the blower motor.


----------



## how (Feb 26, 2011)

By the rough timing of the sound ending one minute before the blower stops, I'd be looking at a gas orifice whine.
A manometer check of your gas valve or manifold will tell you if your pressure is too low. If your furnace is an 80% with the burner orifices exposed through the venturi burner throats, a tech can cover one of those orifices with his finger and if the sound disappears, its a pressure issue.

Depending on the type of blower motor and how long it takes to it wind down, if removing the furnace filter removes the sound, then the sound is from something different.

Let us know.


----------



## gma2rjc (Nov 21, 2008)

how said:


> By the rough timing of the sound ending one minute before the blower stops, I'd be looking at a gas orifice whine.
> A manometer check of your gas valve or manifold will tell you if your pressure is too low. If your furnace is an 80% with the burner orifices exposed through the venturi burner throats, a tech can cover one of those orifices with his finger and if the sound disappears, its a pressure issue.
> 
> Depending on the type of blower motor and how long it takes to it wind down, *if removing the furnace filter removes the sound, then the sound is from something different.*
> ...


Thank you How. I pulled the furnace filter out a little bit. As soon as I did, the noise stopped. When I pushed it back in, it made the sound again. 

When I lifted the bottom corner of the filter a little bit, it stopped again. It sounded like the noise was from air being pulled in through the opening where the filter fits in. When I put my hand down there, I felt air being pulled from the room, into the that opening.


----------



## biggles (Jan 1, 2008)

the furnace will pull the easiest air closest to the supply return so it is whistling thru the access panel just tape it over...i was going to tell you to take a hammer sideways and bag the return duct the lenght of the run...bet if you cover the return grill in the space the noise will diaappear....returns are always the crazy noise area first to check


----------

