Wobbly attic exhaust fan

Old 05-18-13, 09:54 AM
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Wobbly attic exhaust fan

Hi, fellow DIY-ers. I'm setting up summer cooling in my house, which doesn't have central air, and we make heavy use of an old exhaust fan installed in a window in our attic.

We maintain it to some extent; the belt's new and in good shape, and we goose it with motor oil. However, when we turn it on, it seems to clack, and the wheel at the fan end of the belt (i.e. not the drive wheel) seems to wobble somewhat. I'm including a video at this link, and can provide more detail if need be. Can anyone diagnose this problem? Thank you.

Here's the video. It's best viewed in high-def on a large screen: Diagnose this exhaust fan - YouTube
Old 05-18-13, 11:23 AM
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Welcome to the forums.

That's a pretty old piece of mechanical equipment there. Seems to spin pretty slow for exhaust fan duty. Hard to tell what the issue is. If I had to make a diagnosis based on what I hear/see I would say it's the bearing closest to the belt.

Have you tried to change the belt to see if it's just belt noise ?
Old 05-29-13, 08:07 PM
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What you have there is a vintage Homart window fan. They were a Sears brand, and were built from the 1940's through the early 1970's. They're excellent fans, moving a LOT of air very quietly and at low speeds. I just watched & listened carefully to your video, and the problem is belt related. Is the tension right- not too loose & not too tight? Are you sure the belt is smooth without rough edges or seperations? Also check the alignment between both pulleys.Let us know if you have any questions!
Old 06-10-13, 03:21 AM
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I recently did an overhaul of my parent's old Homart attic fan this winter. It was in dire need of a cleaning, a new cord, a new fan belt and oil. It too made noise but it was a result of the old fan belt and the grill wasn't seated properly. There are two types of belts you could purchase (3L370 or 4L380); I went with the 3L370 which fits snug within the grooves of the pulleys. I would assume that the oil that you added was put into the two (MISSING on your's) screws that are in between the pulley and the fan blades. I'm not sure what kind of motor you have but the motor on my parent's fan requires oil too. It is recommended to use Zoom Spout Oiler (not regular motor oil) on both the motor and fan/pulley shaft. You may want to try and remove the oil in the fan/pulley shaft, clean it out the best you can, go to a local hardware store and find the proper size screws and lastly add Zoom Spout Oiler. I purchased the Zoom Spout Oiler at a Johnstone's HVAC Supply or you could order it over the Internet. Also, for the pulley and the fan blades did you ever try to remove and clean them; then hand spin and finally Allen Key tighten them? Plus are all other bolts tight too?


Image 1: Fan Shaft Assembly Before
Name:  Fan Shaft Before.jpg
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Image 2: Fan Shaft Assembly After
Name:  Fan Shaft After.jpg
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