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Are The Multi-Taps on a Blower Run or Common?
Here's the first question: Does it really matter if the speed taps on a motor are run or common? Well, yes… sort of.
In some cases, it helps to identify if you're dealing with an open winding or an open thermal overload. The thermal overload breaks common, but you will still read a path between Run and Start with an ohmmeter.
Also, I had always stated that the same leg of power that feeds run also feeds start. That's just a simplistic way of saying that the leg of power opposite the start winding on the run capacitor should be fed from the same leg of power as run and the opposite leg as common.
The other thing I always said is that common isn't really a “winding,” but it's a point in a winding.
What I learned is that in the case of a multi-tap blower, the speed taps actually are “common” because they are connected to the opposite side as start. They ALL break when the motor overheats.
Here is a video link to where Nathan and I prove it – https://youtu.be/SaTdFsOUFS4, and yes, Nathan was right