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Pedestal fan stopped working - capacitor issue ?

praaspn

Aug 27, 2020
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I have never repaired a fan but thought let me try. I thought the capacitor may have gone bad as the fan was running slowly and eventually completely stopped working. No humming noise.
It had 5.5 uF 250VAC. Got a new one 5 uF 250VAC. Tested new capacitor for continuity test, didn't hear a beep. Checked with resistance, did not show any values. I do not have capacitance meter. Still, replaced it in the fan but fan did not start. So, 1. Is the new capacitor bad ? 2. Is it possible to test the fan by joining the wires without capacitor and see if it works to isolate the issue ?
 

Bluejets

Oct 5, 2014
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5,883
The bearings usually jam up with dried out oil and gunk.
Fix is to dismantle and clean the shaft, back and front, reoil the bearing wick pads and reassemble. Shaft should rotate really free so try before powering up.
 

praaspn

Aug 27, 2020
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I will re-check the shaft rotation. In my first round of testing, I felt it was smooth. If the bearings jam up, wouldn't I hear a humming sound ? Also, is it safe to short the wires cut off from the capacitor (for testing) ?
 

Bluejets

Oct 5, 2014
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Being such a small low torque motor you may not hear any unusual "buzzing sound".

99% of the time it's the bearings dried out so look at that first.
Save your mucking around bridging out capacitors which will do nothing only make matters worse.
Cap is required to give rotational force.

Most $30.00 multimeters these days have a capacitor range included so if you find the need to test the cap, go that way.
Make sure the capacitor is discharged before placing on the meter.
I use a standard 1K5..5w resistor for multiple applications.
 

praaspn

Aug 27, 2020
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I just bought a multimeter kit for $ 30 a week ago or so...and it does not have capacitance testing...Since I am within the return window, i think I will swap it out to the one with capacitance (whether I need it for this project or not).
 

praaspn

Aug 27, 2020
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Cleaned up the front and back of the bearings, put some 3-1-one machine oil drops, gave a good spin. Assembled it back. Tried with new capacitor, original capacitor or lastly bridging out capacitors. Nothing helped. No movement, no sound. I checked the new capacitor in the new capacitance multimeter. It shows the expected 5 uF value. Wondering now, what else I can check. Visibly, winding looks ok. Not sure if there is any fuse in it. Thanks for your time for responding.
 

Martaine2005

May 12, 2015
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Probably a silly question but is power getting to the motor?

Martin
 

Bluejets

Oct 5, 2014
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As you have a multimeter, check for a circuit across the fan plug pins to start with.

Does the fan have 3 buttons for speed control?

Not uncommon for the flex wire to break where the fan oscillates so start at the plug and work your way through.
 

73's de Edd

Aug 21, 2015
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Sir praaspn . . . .


With the minimal information you initially supplied to work with, just see if this supplemental info will let you get things cooled down again.

I found a fans relevant schematic wiring diagram that basicaly should replicate your unit after my making some alterations to it..

" the fan was running slowly and eventually completely stopped working "

That initially suggests that this is YOUR unit and not being a "curb find" that was picked up by you and then found to be failing . . . but you did not say how long . . . .months . . .weeks . . .days . . . .before the units onset into its non working state.

There could be two manners of the wiring in of the units power on / off state . . . so I just offered those two options.

Look at the power loop that has to be made by my drawn in BLUE ARROW path.
What I really-really-really THINK . . . .that your problem is going to be, is a one shot thermal fuse that opened when you experienced the units motor slowing down, with its conjunct thermal heating of the motor proper. It will be physically located down in thermal contact with the motor windings .

As you can see, the capacitor is just being responsible for giving the motor rotor an initial " PUSH start " in the correct direction at power up. Then the run winding(s) take over.

There was reference to " bearings " . . . . . what I fully expect to be found will be a set of porous bronze sleeve bushings that have two felt pads nestled around them, that were saturated with oil back on motors day one.
Time has run out and the felts are now bone dry and after some run time friction between the motor shaft and bushings heats and expands the pair into a gradually incrementing braking action and ups the motors power consumption, along with a speed slow down. Generated motor windings heat has then popped the thermal fuse open.

In a no power applied test you can see that using your meters low ohms function , and the power switch placed in its on position . . . . . you should read the run windings resistance from blade to blade of the AC power plug.

So now if you find that to be the case, you can then jumper that open unit to be able to see if the fan will not overheat for a 15 min run test. Then,a 1 hr closely supervised test .. . . if no overheating . . . . you lucked out in not having shorted windings developed from insulation enamel breakdown. Shorted turns will zoom up the current consumption.
If all is well . . .cool . . . . then you source and replace the thermal fuse by its written on temp spec.


Thaaaaaassssssssit . . . . .

REFERENCING . . . . . .

upload_2020-8-30_5-21-52.png






73's de Edd . . . . . .


If the all things were fully logical . . . . it would be the MEN who would ride horses sidesaddle.
.

.
 

praaspn

Aug 27, 2020
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Aug 27, 2020
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Thanks. I will go through the above suggestions. Just to answer the question - yes, its my fan(not curb find). It has been running slowly for years but here in California, we don't need to use the fan, so wasn't bothered other than cleaning the dust and trying. (My other fans which were slow became normal just by cleaning the dust from blades etc). But started using this bad fan more in the recent heatwave. felt that its motor cover was feeling slightly hot(compared to other fans) while it was spinning slowly. It ran like that for few days in this round of usage and then died completely.
 

praaspn

Aug 27, 2020
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Aug 27, 2020
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Its a 3-speed switch. With switch in any of the on position, it does not show any resistance reading in the multimeter across the plug pins whereas my other working fans show a value of about 185-190 Ohms.
 

praaspn

Aug 27, 2020
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when i bypassed the thermal fuse, it started turning on. I haven’t tried the 15 min, 1 hr test yet to see if it heats up. once i get the replacement part, i wonder if i will be able to repack it in that compact space !
 

Bluejets

Oct 5, 2014
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Anywhere on the stator should be ok.

Word of warning, crimp the connections , do not try to solder otherwise you will have an open circuit thermal fuse once again..
 
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