House fan.

I'm talking about the regular desk or standing fan used simply to circulate air.

When these fans start getting 'old' they slow down and can't maintain the speed when new. They also give trouble starting up sometimes.

What is the cause of this? I've opened a few of them and have neither see nor smelt burnt wires. Usualy I clean out the old grease and apply some fresh grease to the moving parts. This helps a little but, not for long.

Q1) What is the purpose of the capacitor (condenser) in there?

2) Why do you think the fan slows down?

Thanks

The capacitor is for starting. A simple inexpensive motor would need you to physically give it a spin to get it going once you apply power, or it would just lock in place without the capacitor. The capacitor causes the power in 1 winding to shift slightly in phase during startup and lets the motor begin to spin and then once spinning it will keep spinning. (ok well technically it's not really a change in phase but a change in the inductance of the circuit causing the voltage to current rise in that coil to shift from the other ) So a dying capacitor will cause starting problems. You can replace it, but be sure to discharge the old one first as it will still be storing significant energy even if it no longer has enough capacitance to start the motor.

The other most common reason they slow down is that the bearings start to go bad. I had my attic exhaust fan sieze up completely last summer and I temporarily replaced it with a couple of regular box fans in the vents until I could get around to replacing it. I suppose that with a good quality motor you could replace both the bearings and the capacitor, the windings wont go bad unless they overheat and warp or something, but it's easier to just buy a new motor.

Good thing you clarified that when you did. The title caught my attention as to mean the television show on Fox called House. . .Enjoy!

the motor bearings do not use grease on modern fans.
the cheap oil used in the cheap plastic ones turns to goo and causes drag.
i take the endbells off and wash the bearing and its packing with carb cleaner to get the old oil out.
let the cleaner dry out and saturate the packing with a good quality synthetic oil like mobile 1 ,redline,ect 5w30.
reasemble and its good for another few years.
did it to a 20 year old panasonic 5 years ago and its still good.
i have a western electric from the 20's i just did this to.
it works better than any plastic cheapie and makes no annoying noise.

Snakebite's 100% right, assuming the fan you're working on uses sleeve bearings. It's just the oil gumming up. Clean with some kind of solvent like carb cleaner, naptha, kerosene, etc. A good machine oil is fine if you don't have any synthetic sitting around.

On the other hand, if it uses ball bearings you use grease. Although they're not likely to be servicable without some effort.

I love the old fans. Work better, quieter, and don't pick up dust in the guards (they don't have them). I just wish I could use my 'teens Polar Cub more often--the brush motor plays hell with TV and radio reception.

'endbells', 'sleevbearings', maybe. Our el chepo fans do not have bearings as in balls and cup or any rolley things in there. It's just the shaft of the motor inside of a 'hole' with light grease.

Snakebite, ABTOMAT, yeah, I did assume that it was the old grease gumming up and have cleaned it many times. I've used from grease to thick oil to thin oil to lube the motor shaft but, it helps little. And in my opinion, 20 years ago, any fan made would be many times more durable than the average priced fan available today.

James, I'll try changing the capacitor to see what happens though I have my doubts.

From what you describe, if the capacitor wasn't present, you'd have to spin the blades to get it going. Once spinning, I assume that full speed would be achieved quickly. What's observed is that if the fan is slow to start spinning (you can hear the motor straining) and you give it a little help, it does spin faster but not at full speed and the motor is still heard straining slightly. :shrug:

I'll let you guys know what's the result.

Thanks.

the hole is a sleeve bearing and uses oil not grease.the endbell on that one would be a potmetal assy held by the thrubolts.bearing is in its center.
i bet if you follow the cleanup instructions it will work fine.
and the cap is for low speed in the cheapies.if open no low speed.
if shorted low will be same as high.after the cleanup and drying off the solvent i just drop the endbells in a cup of oil that submeges the bearing and packing.
the bearing is a porous bronze called oilite.it needs to absorb oil.let em soak overnight and wipe them off well before intalling.

The capacitor is for starting. A simple inexpensive motor would need you to physically give it a spin to get it going once you apply power, or it would just lock in place without the capacitor.

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I shorted the capacitor, in effect taking it out of the circuit hoping that manually spining the blade would start up the fan. It didn't work. The humming got louder and when I spinned the blade, it slowed down fast. Hmmmmmmmmm

I think the motor you are dealing with is a PCS (Permanent Split Capacitor) motor. The Capacitor is there to make a 90 degree phase shift for the start winding to get the rotor spinning. When you shorted the capacitor, you put both the start and run windings in the same phase. I think the back EMF of the start windings when put in the same phase is what slows down the motor.

I played with my own fan just a few mins ago and if I unsoldered the capacitor, the motor won't start unless I twist the shaft.

I have an old fan that is acting funny too. On low it slowly spins, sometimes stops and it hums louder. I will try to spin it by hand and receive the same slowness and more buzzing. If i switch to high it will wirl up to speed, then I switchto low and it will run on low til i turn it off.

I figured since i use this fan all summer long and yearly to keep me cool while working out that I would just replace it.

Also check for pet hair and human hair gunking up the shaft. I like fans, liked 'em ever since I was 5. I've had a couple of antique fans over the years. The oldest one I currently own is an '80s vintage Galaxy 12" blue oscillating fan.

On my wish list:
The early '80s vintage KMart box fans (with the blue-violet sides)

CHC said:

Good thing you clarified that when you did. The title caught my attention as to mean the television show on Fox called House. . .Enjoy!

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And I thought he was talking about House music....