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greybeard851 · Sep 8, 2007, 02:48 PM

Hello,

I have a 50-some year-old box fan that was my mothers. It stopped working and I found that where the power cord entered the fan the wiring broke exposing bare metal. I replaced the wiring, observing the wiring pattern before I removed the connections. It was rather simple in that there was a push-on clip on each end of the power cord. When I pulled them off, that left only two male parts to push the new clips onto. On one side (I'll call HOT) (this was made well before polarized plugs were thought of) the clip attached to a thermostat and there was a second wire attached to that female clip which went to the pilot lamp.

There is a series of switches that control the three speeds and the directions, also a condenser (er... sorry, capacitor) to start the motor. I checked to make sure that none of the other wires/clips had come loose and everything else looks correct. I replaced the old power cord with the same size (18/2) and bought a squeeze-on plug at HD. Logically, the darned thing should work. I even tried reversing the plug in the AC to see if the spot I called HOT should have been the neutral thinking that this would put the HOT on the other side if needed.? When I turn on the fan it buzzes and if I give the blades a spin, it will sort-of run at half speed. The pilot light does not come on until I turn the thermostat down, which shuts off the motor. Weird.

Can anyone see something I may have missed, or tests I can run to check it out?

Any help would be appreciated.

Thanks,

Grey

MOWERMAN2468 · Sep 8, 2007, 03:05 PM

Turning the thermostat down means to make it cooler, thus the light coming on and the fan should run. Sounds like you have brushes that need replaced. Was the fan running before you replaced the cord?

greybeard851 · Sep 8, 2007, 04:48 PM

Mowerman...

Actually, watching the leaf switch as I turned the knob, the light came on when the contacts separated. The fan was running, then one day stopped. That's when I found the broken power cord. I really don't know up from down on this thermostat. All I know is the contacts were closed (Motor buzzing and light off) and then they opened (Motor stopped buzzing and light came on). At no time did the motor start to turn. If I wasn't pretty sure that I had wired it properly, I would think that there is two hots and no ground, or something like that.

Thanks for answering.

Grey

MOWERMAN2468 · Sep 8, 2007, 05:54 PM

No, impossible to only have two hot leads, the motor would not turn at all. You must have a positive and a negative to produce the magnetic effect onto the armature that spins the motor. And perhaps the light is suppose to come on when it is cooled the room to the set temp. the thing is older than I. I still think if you are sure you wired it correctly that you have problems in the brushes.

ceilingfanrepair · Sep 11, 2007, 08:36 AM

Send me pictures of the wiring maybe I can help.

It sounds like maybe some other connection came loose when you replaced the cord.

greybeard851 · Sep 19, 2007, 07:28 PM

Hi Guys,

Sorry it took so long to get back to you but I have been ill lately. Nothing serious (Whew!)

Anyway, Mowerman. I have looked at that motor from one side to the other and there ain't anyplace for those brushes to hide. It must just be a brushless motor. Hey, it even has oil ports for the bearings, Imagine that. What I was referring to about the two hot wires was that it sounds like when there is a bad ground and it's trying but isn't getting enough voltage or something like that.

Ceilingfanrepair, I emailed you the schematic once I found I could not insert the image without it being on the web. If it is too big let me know and I'll email it in a smaller size. I did not actually diagram the motor itself, because that would require taking it apart and I'd rather not do that if I can help it. I just showed the wires that would go to/come from the motor.

Thanks for the help guys.

Grey

letmetellu · Sep 19, 2007, 07:36 PM

This motor does not use brushes, it is probably a shaded pole motor and has very little power, therefore you need to be sure that the fan is very easily turned or the fan will not start it will only buzz, so turn it on and give the blades a turn and see if it will then pick up speed. This fan does not have a thermostat only a speed switch.

greybeard851 · Sep 19, 2007, 07:47 PM

Hi letmetellu,

I tried giving the blades a push and it did run, albeit very slowly. The blades turn very easily because it takes awhile for them to come to a stop when it is shut off indicating low friction. On what I referred to as the thermostat switch it is inscribed "Cool --->" so I can only believe that is what it is.?

Grey

ceilingfanrepair · Sep 22, 2007, 01:44 PM

Older box fans have thermostats, reverse switches, pilot lights, all kinds of features.

It sounds like this is a PSC motor and something is loose or not making good contact at the reverse switch or capacitor.

greybeard851 · Sep 22, 2007, 07:03 PM

I turned on the fan and gave the blades a push and it slowly built up some speed. I'd say between a quarter and a half of what it should be. I selected the lower speeds and it did keep running, albeit more slowly. It ran this way in either direction. I ran it for around two minutes on "high" and it did not seem to get over-warm. Even at that slow speed those deep biting blades were moving some decent air. It'd sure be a shame to throw it out. You don't find quality like this anymore... even if you pay big bucks for something.

Well, enough for tonight. Have a great weekend.

Grey

ceilingfanrepair · Sep 23, 2007, 02:52 PM

Again, that sounds like the symptoms of the capacitor being defective or not being engaged. Check all wiring to and from the capacitor, and check the capacitor itself.

greybeard851 · Sep 23, 2007, 08:12 PM

I was wondering about the capacitor but I only have a digital tester. How would I test the cap and how can I tell what size it is if I need to replace it?

Thanks for the help.

Grey

KISS · Sep 23, 2007, 10:42 PM

The values are written on the cap. Like 6 uf @ 600 VAC. They can also be dual caps with a common lead. Difficult to test without a cap tester, BUT if they read nearly 0 ohms, it's bad.

ceilingfanrepair · Sep 24, 2007, 08:06 PM

Caps rarely short, the easiest way to test them is to replace it and see if that makes a difference.

In this case it would only be a single capacitor with two terminals.

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