Furnace Echo Noise

[Addison]

Hi all. Im not a pro by any means, but a pretty handy DIY guy.
Over the last year, i noticed my furnace making a strange sound when running. The sound (tough to explain) sounds similar to a "wub, wub, wub" sound. Also most like an echoing/pulsating sound.

I took apart the blower wheel, make sure that was clean and also inspected the motor. The furnace is fairly new and everything was super clean. I replaced the Furnace Filter as well. Ive lived in the home for 7years and the sound just started about a year ago.

Strangely enough, if i put the thermostat to "Circulate or ON" to run just the blower, the noise does not occur. Only occurs when either the AC or the Heat is turned on. Any suggestions or ideas would be greatly appreciated!

 

[Fitter30]

Whats the brand,model, serial of furnace.

 

[Sponsor]

 

[Addison]

Make: Carrier
Model: 58STA090

not to sure in the serial; I didn’t not see it any of the labels.

 

[Fitter30]

Air buffering noise is usually caused by duct to small. When the ac is running fan speed is on high and when fan is switched to on fan is also on high, heating is on medium. So im at a loss with switching from auto to on.

 

[Addison]

Im a bit confused as well. I find it strange that i never heard it when we moved in 7+ years ago either. I would think if it was due to air buffering, it would have always occurred. However, i find it strange as well that it doesnt occur when the Fan is turned to circulate or on.

 

[Fitter30]

If you have floor registers possible one or two might have closed, also check return grills if there blocked with dirt. If your filter is in the duct pull the filter see if the buffering changes for a test.

 

[Addison]

check all registers and they are all open as well and clear returns. Changed filter 3x since noticing the echoing as well as tested with the filter removed. Yielded the same results.

 

[Fitter30]

Blower assemblies in furnaces normally not to difficult to pull and inspect. Most are mounted on tracks and only two screws hold them in along with plugs that disconnect the wiring.

 

[Addison]

Blower wheel and motor have been taken apart and inspected. Both were very clean with no signs of warping or damage.

 

[Fitter30]

Furnaces on heat normally run on medium speed by turning fan to on should go to high speed. Compare the noise.