Blower Fan Speeding up and down


  #1  
Old 06-15-20, 02:37 AM
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Blower Fan Speeding up and down

Hi everyone. Looking for some advice on this.
My System :
Furnace - American Standard Freedom 80 Comfort R with Variable speed fan
Condenser - Allegiance 16 4 ton with 2 step compressor.
Thermostat - Ecobee 4


Noticed last night that the blower fan is speeding up and down. Even took a video of it. Link :
https://www.youtube.com/watch?v=KIYJ4T7N2IE

From what I've read online, many refer to the fan relay. I don't think I have a seperate fan relay that can be changed. The blower motor cables hook upto the control board. Image :
https://imgur.com/gallery/fzhmVf6

Blower free spins by hand. Doesn't feel like fan bearings are bad or anything that would cause drag.

So what do y'all think? Motor going out? ECM going out? I have a spare control board... should i try changing the board and see if problem goes away?

Blower Motor - 1 HP 115v MOT09233
ECM - D341314P05

Image - https://imgur.com/gallery/pkOEUHi
Any help would be greatly appreciated
 
  #2  
Old 06-15-20, 10:47 PM
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The blower is supposed to change speeds during operation.
Is it just changing speed during cooling ?
Try dropping the thermostat five cooling degrees.
Does the blower still react the same ?

Those ECM motors can be a problem to diagnose.
 
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Old 06-15-20, 11:25 PM
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The blower changes speed erratically. Stays high for a couple seconds, then low. No matter what the thermostat temp is calling for. The only speed changes i know of with the system is the comfort-r setting. Where it will run the fan at a lower speed at startup for a few mins to help reduce humidity. Then it will ramp up to full speed.
I've ordered a new ECM and Motor. Hoping the new ECM will take care of the problem. If no, new motor going in as well. I realize the system is 14 years old, but knock on wood... it's been pretty bulletproof so far.
 
 

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