The blades keep slowing down to the point where i can nearly count the revolutions and then speeding up back to normal. After it started happening i took apart the fan and did a clean and lube. Improvement for a day or two but behaviour now back exactly as before.

 

If the problem is a bearing in the fan i would expect a constant speed and some mechanical noise. Can the power in the building be the culprit? It's a modern block of units. I don't notice lights dimming or any fluctuations in supply.

Try changing the capacitor.

12 minutes ago, johng said:

Try changing the capacitor.

The "Flux Capacitor"?

 

 

46 minutes ago, csaba81 said:

The blades keep slowing down to the point where i can nearly count the revolutions and then speeding up back to normal. After it started happening i took apart the fan and did a clean and lube. Improvement for a day or two but behaviour now back exactly as before.

 

If the problem is a bearing in the fan i would expect a constant speed and some mechanical noise. Can the power in the building be the culprit? It's a modern block of units. I don't notice lights dimming or any fluctuations in supply.

As 'johng' said it must be a capacitor from about 4,uF and is mounted at the motor.

Yeah, first port of call would be the capacitor.

 

Small fans are about 1.8uF, make sure you get a proper "run capacitor", they are really cheap on Lazada/Shoppee.

 

It's also worth checking your supply voltage (you can't rely on lights dimming as an indicator these days).