Issues with kitchen fan - how to salvage? [closed]

Question

In my kitchen there is a fan to extract air in case it smells during cooking to not make the whole appartment stink like food. When I turn it on, it looks like it is working. But after a bit of time, the sounds it makes change - which seems unexpected.

So I took the blower unit out of its housing. This is what it looks like on its own:

The schematics look like the following (this is what I was able to figure out without opening the fan itself):

I connected it to the mains and let it run for a bit. And sadly it behaved a exactly like in its housing in the kitchen. When the unit starts up being cold, you can feel a strong air flow out of it. After a while the air flow drops to a gentle breeze. This is where I disconnected it from the mains again. I did 2 measurements: First I measured the voltage accross the capacitor: It starts at 280 V AC and slowly drops down. Around 180 V AC there was not much air flow left. What bothered me was that the capacitor heated up. I'm bad at guessing temperatures but it was well above comfortable temperature.

Since I don't have a power analyzer socket, I let it cool down and measured the current it draws. The unit starts at around 200mA. The current exponentially rises. At 350mA you could hear that the motor was spinning slower and at 400mA I disconnected power again.

The label on the fan says 36W which would translate into roughly 160mA. The label on the capacitor says 1,5 uA +/- 10% @ 320V AC.

My multi-meter did not want to measure the capacitor in situ. And since the connectors are crimped and I don't have replacements at hand, I did not want to destroy them, yet.

As the current draw is well above what the unit should have drawn and also the capacitor is getting too hot for my councious, the unit is not getting back into the kitchen anytime soon.

Question: Is this fan salvagable? And if so which component should I replace?

Date of manufacture: 10/1982

Location is Germany, so the mains voltage is 230 V

Edit:

• I measured the capacitor on its own. Also made a technician at a local electronics store measure it. Both measurements came up fine. But that does not mean anything. The fan started blowing fine at first.
• I bought a new capacitor and wired everything up. After 5 minutes the capacitor stayed cool and there was no audible changes in fan speed. Also the voltage across the capacitor stayed between 275V and 280V AC.

Will put everything together tonight and reinstall it. Thanks for the help.

Answer 1

There's a chance the capacitor has simply failed and you can replace it. You'll have to cut one of the wires to measure it. If it has failed it will likely measure much lower than the 1.5uF capacitance marked on it or it may have large leakage due to internal damage. If it has caused the motor to overheat too much, the motor may have been damaged. The capacitor should not be getting hot at all.

In the case of a similar type of draft inducer fan used in our high-efficiency furnace the motor had to be replaced.

Answer 2

The motor bearings may be failing. See if you can determine how easily the fan rotates by hand. Turn it on and immediately turn it off and see how quickly the fan stops turning. Let it run for a little longer and see if it takes the same time to stop when you turn it off. If is comes to a stop more quickly or is more difficult to turn by hand when it is hot, the bearings are probably bad. You will need to judge how much to risk the fan failing while testing. Changing the capacitor is probably the only repair that is worth doing. Even that is of questionable value for something that old. Changing bearings is probably not worth doing. In any case, it is probably better to buy a new fan than pay someone to fix it. It may be better to buy a new fan than to buy parts to fix it yourself.