# Thumping sound from air handler blower motor



## james7679 (Feb 7, 2016)

It sounds almost like a muffled kick drum. It is random. It has no sound pattern. This morning, as I was laying in bed, I heard the heater come on. I could hear the air coming from my vent, as usual, then the thumping noise started and the air would stop flowing and start again.

Unit is a Carrier FV4BNF002, with a 314916-702 Carrier Indy Blower assembly, which has a GE 1/2 hp motor.

I have:
-opened the cover and verified that the cage starts and stops***the cage does appear to wobble quite a bit, but does not grind against the housing
-verified that the motor spins freely by hand
-verified that there are no obstructions
-removed the assembly and visually inspected the cage***from what I can tell, other than the wobble when the unit is at speed, there are no other issues
-checked the motor mounts

I suspect that the vibration coming from the cage is causing the unit to make the thumping noise, like a washing machine. The motor and shaft seem to not bounce or really move much at all while the cage is wobbling.

I cannot get the unit to reproduce the full affect, at this point, once I do, I will upload a high quality video to YouTube for your opinions. At this point, I am stumped.

Any suggestions or tips would be greatly appreciated.


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## throrope (Oct 30, 2015)

If the cage wobbles, the fan bearings are shot and must be replaced, or the fan mounting is shot and must be repaired/replaced.

Most furnace fans are on a slide. I replaced our fan motor not long ago by removing the internal panel with the control wires, and sliding the fan scroll out. The wires had sufficient slack to pull the fan without disconnecting any execept the motor and attached sensors. The motor and fan wheel was held with sheet metal screws. The fan wheel had a screw set coupler. The local parts store didn't have a replacement. I found one on line for about a hundred bucks and had it at my front door two days later with free shipping. A search with your unit's model & serial should find a supplier easy enough. Local guys may not want to help for fear of cutting out their contractor customers, but I never had issue with online sellers.


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## james7679 (Feb 7, 2016)

Here is a link for the video.




This is with the unit set to Auto Fan and Auto Temperature. When the system spools up, the banging starts. After a few moments of banging(the banging coincides with a strange pulsing of the camera, E.M.I.?) the motor slows to a stop and then makes more noise and begins to spin in different directions. Then, finally, the system spools back up and makes the noise at it's peak level.


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## beenthere (Oct 11, 2008)

Could be the module or the motor. Can't tell from here. Try turning the fan to on at the thermostat without the stat calling for heat or cooling. See if it does it then.


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## SeniorSitizen (Sep 10, 2012)

If the wheel and shaft are actually coming to a complete stop as it appears in the video and the motor has ball bearings, I'm thinking the bearing balls are trying to breed and have pups. That would certainly be time for a new motor or at least new bearings.


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## supers05 (May 23, 2015)

That's an ecm motor. Everything except the noise and excessive vibration is normal. 

Make sure that you haven't thrown a counter balance weight. It will also have different speeds, so it may only vibrate excessively at one of those speeds. (not necessarily the highest) read your manual on how to change the fan speeds to test each one with the thermostat set to "fan on" Obviously, if you find a few speeds that work half decently, you'll get bit more time out of that motor. 

PS. That camera effect is cool. I've never seen EMI strong enough to do that at that distance with that size of a motor. But usually motors like that are running smoothly though. 

Cheers!


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## james7679 (Feb 7, 2016)

beenthere said:


> Could be the module or the motor. Can't tell from here. Try turning the fan to on at the thermostat without the stat calling for heat or cooling. See if it does it then.


I tried with the fan only and the vibration and noise was still present.



supers05 said:


> That's an ecm motor. Everything except the noise and excessive vibration is normal.
> 
> Make sure that you haven't thrown a counter balance weight. It will also have different speeds, so it may only vibrate excessively at one of those speeds. (not necessarily the highest) read your manual on how to change the fan speeds to test each one with the thermostat set to "fan on" Obviously, if you find a few speeds that work half decently, you'll get bit more time out of that motor.
> 
> ...


1. I assume you mean the fact that the motor stopped, reversed and started again.
2. Since I don't know how many clips it WOULD have had, if it had thrown one, I'm not sure how to check. It makes sense, but I have no idea what the procedure for adding a counterbalance to the cage or where to get the clips. I am getting a new ECM, at very least. I hear that this is the main issue with these motors.
3. Yeah, I was a bit shocked to see it in action. Didn't know if would toast my phone or not. Seems to have lived through it though.


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## bob22 (May 28, 2008)

james7679 said:


> 2. Since I don't know how many clips it WOULD have had, if it had thrown one, I'm not sure how to check. It makes sense, but I have no idea what the procedure for adding a counterbalance to the cage or where to get the clips.


At 25 seconds into the video, a shot of the side of the blower housing has a hole in it. Perhaps this from a missing clip or someone is shooting a gun in the heater room again!


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## supers05 (May 23, 2015)

james7679 said:


> I tried with the fan only and the vibration and noise was still present.
> 
> 
> 1. I assume you mean the fact that the motor stopped, reversed and started again.
> ...




Cheers!


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