Fixing a seized oscillating fan motor
There are many ways these fans can fail, but if it hums when turned on, and the blade doesn't spin freely, then the problem is a seized bearing -- A very common failure mode for fans like this. In fact, if the fan has not been used for a few years, it's more likely to be seized than not.
So I opened it up. After removing the front of the cage around the fan blade, I loosen the nut on the fan. The plastic nut holding the fan blade is typically a counter clockwise (or left hand thread) nut, which is to say, it needs to be turned clockwise to remove it.
The fan blade then just pulls off.
This immediately allowed the shaft to turn freely.
What happens is that over time, and with a bit of heat, the thinner parts of the lubricating oil evaporate, and the rest oxidizes a bit and turns into a thicker gunk, making it hard for the shaft to turn. Adding some very thin lubricant from the WD40 loosens it, allowing it to turn.
This repair was much easier than anticipated.
WD40 is excellent for loosening stuck parts, but it's not the best for permanent lubrication. So I added some 3-in-1 household oil to the bearings, both front and back, and put it back together. This repair turned out much easier than I expected.
For fans like this, if they don't hum or get warm, the failure tends to be the switch, the power cord, or a blown thermal fuse in the motor.
If the motor hums but doesn't run, and if it's hard to turn, its because the bearings are seized. If it hums and turns freely but doesn't run, then it's probably the capacitor connected to the motor, and if it doesn't even hum, it's the motor's thermal fuse, switch, or power cord.
But by far the easiest to fix, and the most common failure mode is when the lubricant has turned to gunk. So check that first before throwing out one of these fans.
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