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PillMD 03-31-2010 02:27 PM

A/C Blower Motor Seems Slow
Greetings to all,
I am a new member and this is my first post.
My a/c blower motor appears to be running at a slower speed than in the
past. I have a 4 speed Dayton direct drive blower model sc093B. It is wired correct for high speed which is the Black and white wire. All other wires are capped off. I did check the run cap. which is 12.5 uf. it tested out at 10.6, so i replaced it. I did check the new one and it is right on at 12.5 uf.
I also ohm cked the Motor windings.
white to black = 2
Black to brown =35
white to brown =37
Blower motor is clean and turns very freely .
I'm not sure if the Ohm test should have different results ?
What else should I be checking and how ?

appreciate any help on this

beenthere 03-31-2010 03:02 PM

White to black ohm is low.

PillMD 03-31-2010 07:25 PM

Too Low OHm reading
I appreciate your response.
What should the Ohm reading be from white to black ? Is this low reading an indication that the Motor is going and needs to be replaced ?


beenthere 03-31-2010 07:31 PM

Varies with the motor a lot.
But 2 ohms is very low. Indicates a possible shorting of one winding to the other.
Would expect 10 plus.

Motors are inductive loads. So they don't ohm out like resistive loads.

3 legged dog 03-31-2010 07:40 PM

Also check the vanes on the squirel cage for caked on dust. Ive seen the added weight slow a motor.

2 ohms does seem low for a run winding.

TJ_in_IL 04-01-2010 08:17 AM

From the looks of the manual, that motor has oil ports. When was the last time it was oiled? May have something to do with it.


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