Does anyone have a connection diagram for an old (1940's) 4 lead motor. Dual voltage?
Owner says its 120/240 V single phase, 1.5 HP.

Thanks, Roger

Roger,
Is there a chance that this motor may be a multi-speed type?.
Some motors have a seperate Live wire for Low, Medium or High speed.
Only other thing that I can think of, would be that two of the wires are meant for the connection of a Starting Capacitor.
Hope that this is of some help to you.

Don't think so. It's on an air compressor. He got it from his father in law. It was running on 120v, he re wired it to 220 and it won't come up to speed, of course the wiring diagram is missing.

I am just not familiar with 4 lead motors, thought it may be some antique winding method. I do not see any evidence of a starting cap.

Thanks, Roger

Suggest taking it to a motor shop and let an experienced motorguy sort it out. {Check under terminal cover for label.}

Verbal information from a non-motor person should be suspect. A wrong connection may easily smoke the motor before you can get to the plug. An induction motor ‘not coming up to speed’ will soon be a smoker, too.

It's probably a Repulsive Induction motor
(something I know a little of, got a half dozen on the farm).

If thats the case each pair is a winding wired in series or parallel for 230 or 110V operation. The trick is finding the polarity for each, so the motor properly runs.
Direction is reversed by moving the brush assembly.