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I have a Bryant 355BAV042060 natural gas furnace that I had to replace the draft inducer motor assembly on at the beginning of 2018. It's been working fine in the winter seasons since then keeping the house warm. For the last year or so, it's been making a noise when blowing heat. I can hear this noise through the air vents, and also when I'm outside I can hear the noise coming through the furnace air vent/exhaust, echoing off the neighbor's house into our back yard. It's gotten progressively louder over the past. When it's just the fan (circulating air), the noise isn't there.

I took the cover off and it looks like the noise is coming from the draft inducer motor assembly that I replaced six years ago that's making the noise. Here's a video of the draft inducer motor assembly making the noise.

I'm not sure the noise indicates a problem at all, but it wasn't there for the first four years, and it's getting louder, so it seems like a symptom of something not right. I assume the issue is a bad bearing. When the draft inducer kicks on, the pitch of the noise starts low and increases as the speed of the draft inducer does, and when it turns off, the pitch slowly goes down as the draft inducer slows down.

My goals:

  1. Identify the problem. Does a bad bearing indeed seem the most likely cause of the noise?

  2. Identify the cause. In my head, it's possible that a bearing just went bad. But it's also possible that I (regular DIY guy, no formal HVAC training) installed the part incorrectly. I followed the instructions, and used the special Momentive RTV 162 high-temp silicone to seal up the collector box as instructed. But I also starting using MERV-13 air filters maybe 18 months ago, and I'm not sure if that may be too restrictive of a filter for my furnace.

  3. Identify the solution. If this is indeed a bad bearing, is it likely it can be replaced? I've found a couple YouTube videos where people are replacing bearings, and I do have a puller. Or would the recommendation be to replace the entire assembly again.

Updates

  1. The draft inducer motor's bearings are sealed, so no maintenance to perform on them.

  2. Pushing on the motor while it is running does not affect the sound. Video.

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    Is it "permanently lubricated" or are you supposed to be oiling bearings every 6-12 months? If you are not getting overtemp (high cutout) errors, I doubt your filters are a problem, and in any case they should have nothing to do with the draft inducer.
    – Ecnerwal
    Nov 16, 2022 at 16:25
  • Huh, I'm not sure. I don't remember reading anything about regular maintenance on it, but I'll have a look. Thanks!
    – pcronin
    Nov 16, 2022 at 16:27
  • @Ecnerwal - the draft inducer motor assembly is part number 340793-762 and I can't find anything on the internet that suggests I should be oiling any bearings. Here's a link to the installation instructions: shareddocs.com/hvac/docs/1009/Public/07/IIK-340793-762-01.pdf
    – pcronin
    Nov 16, 2022 at 16:46
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    Installation is not maintenance, as instructions go. Normally if meant to be oiled there are oil holes and either stamped in text or labels mentioning the frequency and type of oil. The instructions do bring up the possibility that the noise might be from the fan itself squealing due to contact with the housing, inferred from the "spacer" part of the instructions.
    – Ecnerwal
    Nov 16, 2022 at 22:02
  • Try gently pressing or moving the angle of the fan motor, a very small amount, and see if the noise changes. If so it is hitting the housing. You could remove it and see where it is hitting. The solution could be as simple as remounting it.
    – Gil
    Nov 16, 2022 at 22:14

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From everything you have tried I would assume the fan motor has failed. I recommend you purchase another fan motor after you verify that it is no longer in warranty. Then maybe February when it is real cold you will be able to replace it immediately when it fails. Or change it now an and keep the old for an emergency.

When you remove it, shift it slightly if you can, tighten it then try to see if it then works properly. If not remove it check the fan blade/cage for any wear marks or shiny surface. Good Luck.

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  • I appreciate the advice! I actually do have the old one still. Perhaps I'll focus on repairing that one as a backup. But, I'm not ready to give up on this one just yet. I'm planning to remove the motor assembly from the furnace and spin the motor both electrically and manually. If the noise still happens outside the furnace, and it is indeed coming from the motor, isn't repair still a possibility? I really don't want to pay another US$1100 to replace the entire assembly and discard the old one when a US$20 worth of bearings and a couple hours of time could get me back in business.
    – pcronin
    Nov 18, 2022 at 18:58
  • Check if it's dirty? Does it make that sound away from the furnace? youtu.be/Zax02itYHkU in desperation maybe oil after cleaning it?
    – rogerdpack
    Dec 16, 2022 at 18:21
  • Any luck? Ideas that come to mind are: if you push it while it's running does it change sound? Might be able to get a cheaper one on eBay or just replace the inducer blower wheel instead of the entire motor? Or just grommets?
    – rogerdpack
    Dec 19, 2022 at 18:36

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