# Re-wiring a Dunlap 1/3 HP Thermotron Model #115.5454 Split-Phase Electric Motor



## btvarner (Nov 8, 2019)

Ok, here goes. My first post. Like most 1st postings, I screwed up & need help!

*Background*:
I have a 1941 Craftsman 101.03622 drill press. It is powered by a *Dunlap 1/3 HP Thermotron Model #115.5454 Split-Phase Electric Motor*. My dad bought the press in the 1940’s. I used it throughout my youth & when he died, I got it. Other than oiling it, have not done any other maintenance. The motor is split-phase. Has a centrifugal switch & a thermal reset switch. Also had an On/Off switch in the motor base. At some point, dad had apparently changed the wiring in the drill press. He installed an On/Off switch on the press itself in order to more easily turn the drill press on and off, rather than reaching all the way back on the motor. The new wiring layout removed both the thermal reset & motor base On/Off switch from the circuit. The new press mounted remote switch was also introduced into the circuit directly into the wiring panel through the opening. The 2 prong power cord was also run directly into the panel through this same opening. Other wires were just capped off in the motor base and wiring panel area. Needless to say it is a cluster.

The other day I “touched” the power cord near the motor and sparks flew! The power cord had been rubbing against the side of the panel entrance for years and years. Had finally worn through, and disconnected. As one side of the power cord had frayed through, the motor would no longer work. I removed the motor and re-tested functionality, once I fixed the cord. Works fine. It is such a mess however, that I thought it was time to go through the motor. I have very little experience in rebuilding electrical motors.

*Issue*:
Between the wiring being screwy and a lapse of judgement, I took the motor apart without FULLY understanding how/where some of the stator wires attached. I am not desirous of putting the motor wiring back together the way it was. I want to wire it as it came from the factory. But because of all the changes that had been made to the circuit before I started, I am having difficulty determining how to rewire correctly for re-assembly.

The Thermal Reset switch & Centrifugal switch seem to be in good shape. I bought a new simple On/Off switch for the motor base. I want to rewire all these back as they should be. I seem to be unable to find any wiring diagrams for this motor online.

Especially confused determining which stator windings are for start-up, and which is for running? There are several threads around on this general subject, but none seem to answer the wiring questions for this motor. Hoping I can receive some direction.

I did put the multimeter on the stator. One of the below images show the results of that test. Thanks in advance!


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## markba633csi (Nov 9, 2019)

OK 1 and 5 look like the same wire.  One of the two is probably a "convenience" wire just to reach across, possibly to reach the thermal button.
So 2 and 5 would be the run winding, 3 and 4 the start winding. Start windings are most always higher in resistance than the run.  The centrifugal switch would be in series with the start winding,  and that leg would be in parallel with the run winding. I would probably put the thermal in series with the whole thing (to either #1 or #5, whichever fits better)
That description should get you running again.  Connect power to free end of thermal button and #2 or #5.  If rotation is backwards reverse 3 and 4
Mark
ps I'll do a quick sketch for you shortly


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## markba633csi (Nov 9, 2019)

This might be helpful:  note that the thermal might need to be relocated if it can't support the starting load and trips too easily
there is a mistake in my text:  it should say "connect power to free end of thermal button and #2"
Also, ignore the numbers 1 and 2 on the centrifugal switch- my drawing program did that automatically


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## wa5cab (Nov 9, 2019)

Good drawing.  Note that the relative position of the Start winding and centrifugal switch isn't important.  The lead from 1 or 5 to the start circuit could go to the switch first if that is more convenient.


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## markba633csi (Nov 9, 2019)

Exactly, the relative locations are not critical as long as the electrical orientation is the same I.E. the centrifugal switch could be drawn on either side of the start winding and the result would operate just the same. 
The motor rotation may well have to be reversed by swapping either the start winding ends or the run winding ends
This thread is a good example why it is a good idea to leave an electrical "trail of bread crumbs" when disassembling electrical devices. A few minutes spent making masking tape labels saves much corn-fusion later


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## btvarner (Nov 9, 2019)

Thanks guys, that makes sense.  Here is an overview of how I plan (At this point) on wiring the motor back together.  Let me know if this does not make sense................


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## btvarner (Nov 13, 2019)

Thought I would finish this thread.  I re-wired the motor as described above and all is well.  Thanks!


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