Maker Pro
Maker Pro

Fan making humming sound but not turning - CBB61?

Cirkit

Oct 28, 2015
155
Joined
Oct 28, 2015
Messages
155
I am trying to repair an air filter. The fan just makes a humming sound on any of the three speed settings but does not rotate.

I've measured the 1.5µF motor capacitor (CBB61) and it's around 1.2µF. The tolerance of the capacitor is 5%. Would this be enough to prevent the motor from rotating?

Even if I spin the fan and power on the air filter, the fan still does not rotate.

Could I temporarily add a 470nF Class-X capacitor in parallel with the CBB61 to prove if it is the reduction in capacitance that is preventing the fan from rotating?
 

Minder

Apr 24, 2015
3,478
Joined
Apr 24, 2015
Messages
3,478
Sounds like a PSC motor if so and the cap is defective, it would normally spin up by giving it a spin when powering up.
Measure the two windings, they normally would be equal resistance,
If replacing the cap, it requires a AC motor run rated version.
M.
 

Cirkit

Oct 28, 2015
155
Joined
Oct 28, 2015
Messages
155
Thanks for your reply Minder.

I measured resistances between the 4 colours on the 4-pole connector and also between both capacitor connections to each of the 4 wires (with the capacitor removed):

4-pole connector
Green - Black 458Ω
Green - Red 126Ω
Green - Yellow 297Ω
Black - Red 332Ω
Black - Yellow 161Ω
Red - Yellow 172Ω

Capacitor connections (Grey & White)
Grey - Green 215Ω
Grey - Black 672Ω
Grey - Red 341Ω
Grey - Yellow 512Ω

White - Green 458Ω
White - Black 0Ω
White - Red 332Ω
White - Yellow 160Ω

I'm guessing the configuration is something like this for the three speeds:

pscms.gif
 

Minder

Apr 24, 2015
3,478
Joined
Apr 24, 2015
Messages
3,478
That would be the typical hook-up.
I overlooked the 3 spd.
M.
 

73's de Edd

Aug 21, 2015
3,628
Joined
Aug 21, 2015
Messages
3,628
Your readings certainly correlate with 215Ω 's as being the auxillary winding resistance.
If only having that .47 poly X type cap, I would certainly venture shunting it across the run cap and then putting the unit in HIGH speed and giving the fan / impeller / shaft a spin in the CORRECT direction.
If still just a HUMMMMMMMMM, pull / disconnect the original capacitor out from circuit and then just SOLELY use the sub capacitor and go thru the same procedure again.
 

Cirkit

Oct 28, 2015
155
Joined
Oct 28, 2015
Messages
155
Your readings certainly correlate with 215Ω 's as being the auxillary winding resistance.
If only having that .47 poly X type cap, I would certainly venture shunting it across the run cap and then putting the unit in HIGH speed and giving the fan / impeller / shaft a spin in the CORRECT direction.
If still just a HUMMMMMMMMM, pull / disconnect the original capacitor out from circuit and then just SOLELY use the sub capacitor and go thru the same procedure again.

Thanks for the suggestion. I temporarily replaced the motor run capacitor with a Class-X2 one that I had of slightly higher capacitance and the fan worked!

The one on the left is the original capacitor and the one on the right the X2 temporary one I tested:

Poly caps.JPG

So what is the difference between a run capacitor and X2 capacitor?
 

Bluejets

Oct 5, 2014
6,938
Joined
Oct 5, 2014
Messages
6,938
x2 is a mains rated capacitor, can withstand high voltage peaks.(2.5kV)
 

Minder

Apr 24, 2015
3,478
Joined
Apr 24, 2015
Messages
3,478
AKA Metallized polypropylene material, high insulation and suitable in withstanding over-voltage stress etc.
M.
 
Top