Mark VII Rehabilitation

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The Mark VII AO Smith motor have 6 wires coming out of the motor casing. The capacitor and start switch was still connected to one of the leads. I did a ohm reading on each set of leads for two motors which was the same. The one set going to the capacitor had 1 ohm, another set had 1 ohm and the third set had 6 ohm resistance. Now, I always found the start windings had twice or more resistance then the run windings. I believe that the motor will still start and run with the start and one run windings in parallel but I have to question what I found on these 2 motors. I did not find any references in my files as to what which set of wires goes to the start and run windings for the Mark VII AO Smith motor. Does anyone have any diagrams or material as to what wires are connected to the run and start windings? Thanks.

Try this for starters https://forum.shopsmith.com/viewtopic.php?t=2907 Post # 13

I will look further.
https://forum.shopsmith.com/viewtopic.php?t=2907

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Assuming the motor wires are BLacK,WHite,REd,YEllow,White/Red tracer,White/Grey tracer, then:

Run = BLK,WH

Start = RE,W/R

Cap = YE,W/G

The internals of the cap circuit is unknown, but, I would expect one wire goes to one side of the run winding, and the other goes thru the start switch to the other end of the run winding.

So black to white = 1 ohm
yellow to white/grey = 1 ohm
red to white/red = 6 ohm

Please verify!:)

[billmayo]

Assuming the motor wires are BLacK,WHite,REd,YEllow,White/Red tracer,White/Grey tracer, then:

Run = BLK,WH

Start = RE,W/R

Cap = YE,W/G

The internals of the cap circuit is unknown, but, I would expect one wire goes to one side of the run winding, and the other goes thru the start switch to the other end of the run winding.

So black to white = 1 ohm
yellow to white/grey = 1 ohm
red to white/red = 6 ohm

Please verify!:)

Yes, but I question the cap going to a run winding. I checked 2 different AO Smith motors that had the same wiring connections. Ths motor has a external start relay like some 3/4 HP motors. The cap was connected to terminal 2 of the start relay. I will test the motor after this weekend as I have a Home Show booth to staff. I will assume the 6 ohm windings are the start windings and parallel the other sets of run windings and see how hot the motor gets or what else will happen. Sometimes I question what I find when I find no supporting material.

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Yes, but I question the cap going to a run winding. I checked 2 different AO Smith motors that had the same wiring connections. Ths motor has a external start relay like some 3/4 HP motors. The cap was connected to terminal 2 of the start relay. I will test the motor after this weekend as I have a Home Show booth to staff. I will assume the 6 ohm windings are the start windings and parallel the other sets of run windings and see how hot the motor gets or what else will happen. Sometimes I question what I find when I find no supporting material.

Hokay! External start relay! I will search for the pertinent thread(there is one!). But IIRC that was a GE motor! ???????

I would NOT parallel the lead pairs that measure 1 ohm.

The Mark VII requires the start winding to be connected externally since reversing direction can only be accomplished by reversing polarity of the start winding. Thus the wires that are parallel with the run winding need to connect to the cap in series with a start switch(either internal mechanical switch or external start relay). The start relay does not respond to a start polarity change differently.

Did your motor leads match color wise and resistance wise as I described above?

[billmayo]

The wiring colors match for most of the wires. This is what the 2 AO Smith motors I have:

white to white/black stripe = 1 ohm
yellow to black = 1 ohm
red to white/red stripe = 6 ohm

The capacitor is connected to the white/black stripe wire and to terminal 2 on the start relay.

I know the motors were operated with this wiring setup but I question if it was the correct setup. I will test the motors next week with what I feel is the correct connections and see what I find. The many hundreds of motors I have worked with over the years has the start windings having 2 to 3 times more resistance than the run windings. I worked in a motor repair and rewind shop for some time 40 some years ago and still believe the above.

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The wiring colors match for most of the wires. This is what the 2 AO Smith motors I have:

white to white/black stripe = 1 ohm
yellow to black = 1 ohm
red to white/red stripe = 6 ohm

The capacitor is connected to the white/black stripe wire and to terminal 2 on the start relay.

I know the motors were operated with this wiring setup but I question if it was the correct setup. I will test the motors next week with what I feel is the correct connections and see what I find. The many hundreds of motors I have worked with over the years has the start windings having 2 to 3 times more resistance than the run windings. I worked in a motor repair and rewind shop for some time 40 some years ago and still believe the above.

I found the diagram I mentioned earlier - it was an A O Smith motor after all.


https://forum.shopsmith.com/viewtopic.php?p=81228&postcount=4


I will add a link to the thread shortly. https://forum.shopsmith.com/viewtopic.php?t=6983&highlight=relay

There is a lot of confusion in the earlier posts. (much from me!!!) That thread was a learning experience for me!!!


I think resistance measurements will also yield I just checked my Aosmith int start switch motor (just acquired) and that is what I measured.

White to Black 1 ohm
Yellow to white/black 1 ohm

And White to yellow 0 ohm
black to white/black 0 ohm.

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Looky what I found when I finally looked at the parts manual!:)

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