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By navillus5
#200225
I was tasked this evening with a request to fix my son's window fan. It is a dual fan unit with a three position switch - Off, Low, High.
I thought that it would be a simple fix - a loose wire or a broken switch - no such luck. So I am now on a quest to figure out what has happened to this "simple" device.

The unit contains a pair of two-speed shaded-pole motors that are controlled by a three position rotary switch - I have included photo of the motor and a wiring diagram below. I have not been able to find that much information about two-speed shaded-pole motors, but I would think that the three wires indicate a motor winding with a middle tap. I have measured the resistances between each wire and there is only continuity (11.3 Ohms) between the red and blue wires. This is the case for both motors.

If I connect the red and blue wires to ac power, the fan runs but it also gets very hot, very fast - definitely not a preferred operating state.

So my question is - am I missing something obvious, or did both motors fail in the same way at the same time?
As I finish writing this, my wife popped her head in to tell me that some of the Amazon reviews for this item mentioned sudden failure. :shock:

Any insight would be appreciated!
shaded-pole motor.jpg
wiring diagram.jpg
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By n1ist
#200226
Both motors are in parallel, so an overvoltage could have blown both at the same time, or possibly the same mechanical fault exists; there may be a broken connection from the black or red wire to the winding. The two connections are black/blue and black/red. blue-to-red isn't rated for line voltage; that's why it gets hot.

/mike
By navillus5
#200390
Thanks for the reply. I got busy with other stuff and my wife bought a replacement fan, so I almost forgot to check for a reply to my post!

/Dan
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