Sears compressor doerr motor

by Neil Cunningham
(Hickory NC)

Ok.. bought this Sears unit couple weeks ago.. the pressure switch went bad and I have replaced it. Unit worked fine yesterday when I used a sander on it. Today worked fine and I turned it off to plumb some air fittings. When I fired it up nothing dead... no hum, no noise dead.


So to test the motor I jumped the pressure switch so the 240 was on the motor. I checked voltage At the motor terminals... 240 volts.

I have not checked the caps but this motor is old..

Any advice on checking to see if it is a dead horse?

Also I looked into some replacement motors and a question arises.

This motor is listed as a XM56 frame, 3450 rpm, 5hp but only 15 amps.

So I have read that since it is a 15amp motor it is not truly 5hp..

So would replacing this with a true say 21amp motor increase my CFM?

I have also read that putting a 3hp motor running at 1700rpm but increase the pulley on the motor to make the pump run at 3450 rpm would save power and run the motor cooler.

Any help on figuring this out is greatly appreciated.

Comments for Sears compressor doerr motor

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May 10, 2018
Doerr motor problem
by: Doug in s.d.ca

"This motor is listed as a XM56 frame, 3450 rpm, 5hp but only 15 amps.

So I have read that since it is a 15amp motor it is not truly 5hp.."

For sure at 120v, but you're on 240, so it's close.

I'd go ahead and check the capacitors, the motor is probably fine.

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