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new noise heard when heat comes on

I'm new to this board and to the DIY scene, so I apologize in advance if I leave out anything obvious...

We have been in this house for a little over a year. The house itself was built in 1982 or 1983 (at the moment I cannot remember exactly which one). The heat pump unit outside the house is a RUUD Achiever 9, according to the label on the top, and the blower unit inside the basement looks to be a GE. The model number printed in the metal label is BWV036A100A1. We knew when we moved in that we would need to replace it sooner than later, but we have been waiting to see if it will die while our home warranty is still active.

About two weeks ago I began hearing a noise when the heat was running. When putting my ear to any of the floor vents, however, I was unable to hear the sound. After some checking, I found that the one place where the sound was audible was the return vent on the top floor of the house. The sound itself is a moderately high-pitched wah-wah sound. It pulses rhythmically for as long as the heat is running - at a rate of perhaps twice a second. I am not able to hear it from the return on the main level of the house, or even if I stand near the blower unit in the basement (and I find that part interesting).

Given that this is a brand new sound, I am a little concerned. The question is, how concerned should I be? What might be causing this sound, and what might the best solution be?

Thanks in advance.


Re: new noise heard when heat comes on

could be something mechanical. could also just be something that fell into the floor grate.. do you have kid.. maybe one of them dropped lego's in there

Re: new noise heard when heat comes on

Could be just about everything you can think of. What jkirk said, or a rodent, something loose in the duct, a ball.

Can you remove the register/grill and tell if this noise continues?
Is there a filter at the return?
Is the grill secured with 4 screws tightly?

Re: new noise heard when heat comes on

Thanks, guys. I do have a son, but if anyone would be dropping things down floor vents it would probably be our cat. The return grate is screwed firmly into the wall, at a height of about 5', so it's doubtful that anything was put in there accidentally. Either way, I'll remove it and see if that changes anything.

Re: new noise heard when heat comes on

I wonder if a fan motor bearing is going up or if a duct came loose.

Re: new noise heard when heat comes on

If you can't here the noise at the blower or the first floor then it seems to be related to the return duct on the second floor. It could be velocity noise from a restriction in that ducting only.

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