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NuTone 8663RP Bathroom Vent Fan Bushing

The NuTone 8663RP (for future reference) vent fan in the Black Bathroom began making horrible grinding sounds and, after a day or two, stopped turning. Pulling it out showed the impeller had slipped downward on the motor shaft:

Bath Vent Fan - impeller shift
Bath Vent Fan – impeller shift

Which meant the impeller was now resting on the steel frame:

Bath Vent Fan - impeller interference
Bath Vent Fan – impeller interference

Curiously, there’s no retainer under the impeller preventing it from sliding downward, other than good intentions and a friction fit. Nothing lasts, although it’s been working for the last two decades, so I guess it doesn’t owe me much.

My first thought was to build a steel or aluminum collar with a setscrew to hold the thing up, but I decided to try a simple bushing made of UHMW polyethylene between the motor and the impeller.

Turning it to the proper length required a test fit, then another session on a mandrel made from some aluminum tubing:

Bath Vent Fan - bushing trim
Bath Vent Fan – bushing trim

The snout came out just long enough to clear the motor frame, resting the impeller’s weight atop the bearing around the shaft:

Bath Vent Fan - bushing installation
Bath Vent Fan – bushing installation

It’s hard to see between the impeller blades, but there’s actually a bit of clearance underneath:

Bath Vent Fan - bushing installed
Bath Vent Fan – bushing installed

Which left just barely enough room on the top for the retaining clip:

Bath Vent Fan - shaft clip - detail
Bath Vent Fan – shaft clip – detail

I had high hopes for the UHMW, but it seems any contact between the rotating impeller and the stationary bearing transmits enough sound to be annoying.

So I must break down and build a collar, although it’s off the critical path right now.

As far as I can tell from the pictures, dropping $50 on a new fan unit will get me exactly the same problem. Whether it would last for two decades before failing is an open question, but my experience with freezer fans suggests what we have is as good as it gets and making a bushing is the least-awful way to proceed.

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  1. #1 by Mitch Berkson on 2019-07-31 - 08:16

    An itty bitty flanged ball bearing?

    • #2 by Ed on 2019-07-31 - 15:46

      Minus the impeller, the motor runs dead quiet, so its bearings seem to be in good shape. I think there’s a thrust bearing on the bottom end of the shaft, but I’m heroically resisting the urge to find out.

      The locking collar writeup lies a week in our future, but it’s working fine … [grin]

      • #3 by Mitch Berkson on 2019-08-01 - 08:03

        Right. I was thinking instead of the (too noisy) bushing you made.

  2. #4 by RCPete on 2019-07-31 - 10:54

    Our Broan* bathroom fan got to be quite noisy, and due to our volcanic dust, it was the sleeve bearing in the motor. The electrical/plumbing supply store sells replacement motors, and that did the job.

    (*) Broan and Nutone seem to be shared brands, with shared components. I also had to re-motor the Nutone range fan for the same reason. One of those motors came from Amazon. MTBF for heavy usage is one decade, based on a sample of 2. Note that the range fan motor is not supposed to be swapped by people with large hands.

    • #5 by Ed on 2019-07-31 - 15:48

      I cannot imagine how much fun I’d have around here with volcanic dust: all the exposed bearings / leadscrews / ways in the shop would definitely require more care & feeding than they’re getting now!

      • #6 by RCPete on 2019-08-01 - 12:50

        I haven’t been doing much lathe work lately (FWIW, chainsaw bar oil is a decent way lubricant), but I’ve had to replace lots-o-bearings since we’ve moved here.

        I’m stuck in the comfy chair while recovering from de-bunioning surgery. Stitches out next week, but it’ll be 3-5 weeks until the stainless wires locating the remodeled bones get pulled. It’s about as much fun as it sounds like.

        OTOH, I’m catching up on my reading and researching telescope drive electronics. Want to investigate DIY cameras, too. The CCD for the Cookbook camera is long obsolete, but there may be other good ways to defur the feline.

  3. #7 by captnmike on 2019-07-31 - 12:36

    Would a bit of Locktite(sp?) also work? Or would the friction fit prevent the liquid from getting into the right area?

    • #8 by Ed on 2019-07-31 - 15:52

      If the impeller had a metal hub, I’d be slobbering “sleeve retainer” Loctite on it like there’s no tomorrow. The thing is made from slippery, slightly bendy plastic, probably some flavor of polyethlyene, and past experience says it’ll just laugh off any adhesive.

      On the other paw, the impeller hasn’t age-fractured into a zillion pieces, so there’s that. [grin]

  4. #9 by Grumpy Oldman on 2019-08-02 - 01:14

    how about machining a c-clip groove and using a c-clip on the motor shaft to keep the impeller from shifting. It’s what the factory should have done.

    • #10 by Ed on 2019-08-02 - 14:49

      That’s basically what I tried next: a setscrew in a collar. Turns out letting the impeller loose on the shaft creates an awful racket as it spins slightly slower than the motor. More details in about a week … [grin]

  1. NuTone 8663RP Bathroom Vent Fan: Effective Repair | The Smell of Molten Projects in the Morning

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