Fan motor starts slooooowly


I've seen a number of older exhaust fans that start very slowly. Turn them on, they barely turn for up to several minutes, then finally speed up fairly quickly to normal operating speed. Can anyone suggest why this happens, and a way to fix them to operate properly?
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Bob F wrote:

First thing to try is lubing the bearings I would think
Rheilly P
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If you are talking about the roof attic fans, the motor might be starting to go. They sell replacement motors at Lowes or HD and they are easy to change.
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Mikepier wrote:

Sure, that will fix it but having spent a large part of my work life sorting that sorta stuff I can tell you a lot of the time the motor runs away with no attention until it stops or exhibits the symptoms described. The manufacturers provide ports to apply periodic lubrication which are by and large ignored by the average punter. A slow start is almost certain to be an underlubricated bearing or one that has been worn out by long usage or underlubrication, usually both. Nowadays the cost of professional maintenance can exceed the cost of a replacement (assuming you DIY) so there ya go. For me there is nothing to lose with trying a squirt of light oil on the bearings before spending ya moola :-)
Cheers ............ Rheilly P
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Nope, that's the second thing. First thing is to check for two decades' worth of dirt and crud built up on the blades, and clean as necessary.
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I've seen this a number of times with bathroom exhaust fans. After removing the internal parts and cleaning them thoroughly, performance on many of them improves. Gunk tends to build up on the fan blade which I surmise causes it to be heavier than the little motor was designed for. If not then I replace the motor and blade or install a new and improved (Panasonic) bath fan.
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I assume you are talking about the motors without a capacitor and a start terminal. These motors develop weak torque until reaching full speed. The lubrication gums and the motor spins slow for awhile. It is best to dissasemble the motor, degrease the bearings and apply a light oil (like 3 and 1 motor oil).
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The folks I have worked with tell me that three in one is a poor choice for motors. It (three in one) dries out rapidly. Same with WD-40. The good choice is ND-30 motor oil, or zoom spout turbine oil. The gas mix oil for two strokes is supposed to be good, also.
Cleaning the blade sounds like a wise action, also.
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Cause they're gummed up with shit. Need to disassemble them, clean them with brake cleaner, and relube the end bushings.
s

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