Help identifying wires from antique fan

[thebigjoe1]

Restoring an old westinghouse desk fan from 1919. There are three wires coming from the fan head (motor) labeled G, Y, and R. Can these be identified for me, ie positive, negative, ground? Thanks!

 

[Avo Mk8]

If you connect the meter probes together, does it read something like "0.01", different to OL?
If it does you are not doing anything wrong.
When taking your measurements, "OL" is reporting an open circuit.

You would need to move the fan speed lever to an 'on' posirion to get a reading across the AC input terminals, but with 'OL' across the coil terminals, that's suggesting a problem with the transformer.

Could you just confirm that touching the probes together changes "OL" to a low value reading?

 

[thebigjoe1]

I can confirm touching two probes together gets low reading. Also with the switch in on position, there is still no reading on Ac input terminals..... same with coil.

But, if i keep probe on Hot terminal, and then probe anything else, i get readings from different wires or terminals that i touch (not neutral terminal)

 

[Lucien Nunes]

Please can we test the motor first. It has fewer unknowns and the results can be cross-checked.

With the three motor wires disconnected from the base, test:
Green-Yellow (main winding)
Red - Yellow (aux winding)
Green - Red (both in series, reading should be the sum of the two above)
Yellow - motor body (should read OL)

Please post all four resistances.

 

[thebigjoe1]

With the mutlimeter, am i supposed to touch red to green, and black to yellow? Vice versa? or is there another way. Again, i apologize for my lack of knowledge on how to actually use the mutlimeter.

 

[Lucien Nunes]

For most resistance measurements it doesn't matter which probe is which. Here, for example, the windings are just copper wire so makes no difference which way the multimeter's test current flows through them.

 

[thebigjoe1]

Reading always changes so i took videos and uploaded them. Please see links below.

Green-Yellow (main winding)

PXL_20210713_203337921.mp4 - Shared with pCloud

Store videos in pCloud. Share them with just the right people. Access them on any device. Create a free account now!

u.pcloud.link

Red - Yellow (aux winding)

PXL_20210713_203445328.mp4 - Shared with pCloud

Store videos in pCloud. Share them with just the right people. Access them on any device. Create a free account now!

u.pcloud.link

Green - Red (both in series, reading should be the sum of the two above)

PXL_20210713_203518057.mp4 - Shared with pCloud

Store videos in pCloud. Share them with just the right people. Access them on any device. Create a free account now!

u.pcloud.link

Yellow - motor body (should read OL)
Reads OL

 

[Lucien Nunes]

OK that should not happen. If there is continuity through the windings you should see a steady reading in each case. Make sure the bare ends of the wires are clean and bright, and clamp them securely against the meter probes. If you have alligator clips with your probes, use them. However, if the windings are OK the resistance will be low enough that touching them with your fingers won't have any impact, you'll still get a steady reading. If the windings are open-circuit then what you will see is those variable readings up in the megohms caused by your skin resistance varying.

 

[thebigjoe1]

OK. So i think i know whats going on. The copper leads have a solder coating on them. So what i did was attach some spare wiring i had to those leads, and now things add up as they should per your previous post.

Green-Yellow (main winding)
20.1

Red - Yellow (aux winding)
31

Green - Red (both in series, reading should be the sum of the two above)
51.1

What does this tell us and what are next steps if any?

 

[Avo Mk8]

The figures on the AFCA for your 315745A fan, measured by one member, and corroborated by another, are as below: (Lucien - OP posted similar message on the AFCA showing rating plate)

Between Green and Yellow = 22.1
Between Gren and Red = 52.2
Between Red and Yellow = 31.0

Within experimental error, it tells us your motor windings are likely OK. Good news!

Did you manage to measure between one of those wires and the metal case of the motor (if you could find a bit of bare metal to put the probe on)?

Over to you Lucien ?

Next steps are presumably to investigate the transformer, and why the motor hums when you plug the unit in, when there's apparently no resistance between the plug terminals. Bigjoe - knowing what you now know about resistance measurements, can you check between the coil wires, both red, black, and the switch contacts?

 

[thebigjoe1]

Wire and metal case read 0L as you mentioned it should.

Also, i dont have the A revision of a few years later (which seems to be more common), my model is just 3154745. Not sure if that changes anything with the wiring.

Now if i understood you correctly, this is what i did for my next set of readings

Black coil wire to Switch Contacts

• Speed 1 = 8.4
• Speed 2 = 6.7
• Speed 3 = 4.0

Red Coil Wire to Switch Contacts
- 0.L for all

 

[Avo Mk8]

Now if i understood you correctly ............

Yes, perfect, you did understand. Thank you for the figures.
I haven't come across resistance figures for your earlier version of the fan - only the 'A'. I'm sort of assuming that the motor would be similar between the two, but don't know that for sure. It seems likely based on the similarity of your measurements.

My thought now is that the reason the fan doesn't work is because there is an open-circuit between the transformer and the red wire, or in the coil. I'm rather hoping the red wire might have become detached from a tag or the coil wire. To me the red and black wires don't seem original, and someone has replaced them at some stage.

I'd like to hear Lucien's view now.

Without more thought about your resistance figures, I'm not clear if the red wire is the final end of the coil, as I was assuming, or if it's actually the next tap along from the Speed 3 Connection. I feel probably not the latter.

If it were me doing this I would very carefully investigate what is under that old insulation tape, so see how the red wire is attached, it might be possible to repair it.
But please be careful, as the wire of the coil may be fragile, you don't want to be bending it in all different directions while investigating! If the wire breaks off it becomes much more difficult to repair!

Another view of the circuit I found:

 

[Avo Mk8]

Looking back at earlier post #4, if you plugged the fan in to power while wired as per your diagram, that would have put mains voltage across that part of the coil that now appears open circuit. So I'm afraid it's possible the transformer will need rewinding, or replacing if you can find one.

 

[Lucien Nunes]

Agree 100% with AVO. If the red and black wires of the transformer were connected to the line cord terminal screws and powered up, the secondary (output) winding of the transformer would have been fed with 120V AC which it is not designed for. You are now reading open-circuit between red and black which suggests it has burnt out, or again as per AVO if you are very lucky it has a broken connection where the enamelled or silk-covered winding wire meets the new red PVC-insulated tail. In either case, the transformer is not delivering output to the motor's auxiliary winding so there is no phase-shifted magnetic flux to produce torque. This is why the motor hums but doesn't turn.

Carefully dissect the connection to the red wire to get back to the connection with the transformer winding itself. Don't be surprised if it disintegrates in your hands!

 

[thebigjoe1]

thanks guys, i hope this wasnt my fault because of my impatience in trying to get this to work! I will get to this later today and just hope that the red wire is disconnected and is a simple fix. I do feel that i may have burnt it out, there was smoke coming from the coil at one point, which again was only for a second before i disconnected, but im sure that was enough. Ill post my findings later.

In any event, as a just in case, i have found a couple of A versions of this fan for very cheap, supposedly in working condition. If the transformer itself is shot, i like to transplant a working one over. I assume that should work as a last resort?

 

[Avo Mk8]

In any event, as a just in case, i have found a couple of A versions of this fan for very cheap, supposedly in working condition. If the transformer itself is shot, i like to transplant a working one over. I assume that should work as a last resort?

Yes I think transplanting a transformer from a similar fan should work, hopefully even from an 'A' version.
Bear in mind it's 100+ years old, and probably rather fragile!
If you could swap the switch part of the base containing the transformer over from another fan, so you don't have to extract the transformer and disconnect it from all the switch studs, you would stand a better chance of keeping connections in a good state!