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I installed an AC blower motor into a cabinet to act as a ventilator for some electronics. Thankfully it has a wiring label. Based on the label, it must be a run capacitor induction motor. It specifies a tiny 0.6 uF capacitor. I bought a cheap one off eBay.

This is the fan and a picture of the wiring label:

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This motor has two blowers on the same shaft. They are a typical centrifugal style. I connected the run capacitor across the yellow and red wires. I connected the mains hot to the black wire. The neutral is connected to the blue wire. You can see the little capacitor in the picture as well.

Here is what happens when I power it up

  1. It turns on and spins up very slowly. I think the slow spinup is normal. When the motor is running the RPM alternates very slightly between two distinct RPMs. Its noticeable because the pitch of the noise changes.

  2. It doesn't start on its own, but if I bump the motor it will spinup and start running like case 1.

Do I have this motor wired correctly? Is the RPM "hunting" normal? Is it possible the motor is bad?

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  • \$\begingroup\$ the bare end of the white wire should be insulated \$\endgroup\$ – jsotola Jul 28 '18 at 19:17
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    \$\begingroup\$ Does it run freely when turned by hand, or is there an unusual amount of friction that makes it stop immediately? You can always try a 1 uF start cap. \$\endgroup\$ – Jeroen3 Jul 28 '18 at 19:36
  • \$\begingroup\$ Don't buy cheap stuff like this off ebay unless you can verify the source. \$\endgroup\$ – Andy aka Jul 28 '18 at 19:41
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I suspect the capacitor is supposed to be 6uF rather than 0.6uF. There is a "." after "CAP" in another place.

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If it is that wrong the motor will likely get very hot after a while.

This is similar in value to the inducer blower (not main forced-air blower) run cap value in a home natural gas furnace.

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