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The air conditioner Family FSA-15H has one-phase fan brushless AC motor with 3 constant speeds: High, Medium, Low. After 2 years of rare use, the fan works only on the half of designed low speed: 420 RPM instead of 980 RPM. It heats up quickly and thermal protection shuts the fan off.

enter image description here

I tried to find motor replacement A072 from King Post Industrial. It seems small Taiwanese company which does not deal with private users.

I tried to diagnose the motor:

  • The Capacitor is 5uF as designed.
  • Replacing capacitor to 6uF or to 10uF does not change anything.
  • Applying 220VAC on black-blue, black-yellow, black-white wires gives the same results: slow speed and quick heating up.
  • The motor rotates smoothly, applying extra grease into bearings changes nothing.
  • Measuring resistance of motor coils gives strange results, marked with ?!: enter image description here
  • I tried to search for explanation for 3-constant speed brushless AC motor works but found nothing. Either results for 3-phase motors or for regulated with controller motors.

My question is:

Please, point me to reasonably clear guide to diagnose the 3-speed BLAC motor.

Or, why do I observe that strange resistances of sequentially connected coils?

Ivy Growing
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    Are you prepared to rewind the motor? If not, you've diagnosed it, it's failing. Options are buy a replacement from a different vendor, or send it to a motor repair shop. – Aaron Jun 14 '23 at 17:10
  • It seems the `?!` marks which confused me are the real sign of motor failure. Isn't it? If so, I have to be creative to reach out the motor manufacturer for the replacement. – Ivy Growing Jun 14 '23 at 17:13

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