Fixing brushless extractor motor

Discussion in 'Engineers' Talk' started by ejenner, Mar 15, 2022.

  1. ejenner

    ejenner Active Member

    Got it all slapped back together. The replacement capacitor is a bit bigger but I got it in there with a bit of bending of a couple of bits.

    I cleaned the fan blades as they all had 35 years worth of build-up on them. I thought that would change the sound of the extractor fan and it definitely sounds different.

    What bothers me slightly is I'm not sure if it's powerful enough. Because it sounds different due to clean blades could it also be spinning slower and I wouldn't know? It probably does work to some degree but the tubing goes to the other side of the room to get to the exterior wall. You can see air coming out the exit as there's a cobweb which starts flapping around when the fan is on.

    I think it's job done for the moment. Something is better than nothing and the kitchen will have to be rebuilt at some point anyway. So I'll leave it as it is for now.
     
  2. ejenner

    ejenner Active Member

    Actually, one question, if people are still reading this...

    The new capacitor had 4 pins and the old capacitor had two pins. I just wondered if by any chance it might make sense to join the lower pins to the upper pins on each side of the capacitor or will the output from the capacitor be the same even if only using two of the 4 pins?
     
  3. quasar9

    quasar9 Screwfix Select

    Has the new cap got a diagram printed on its pin config ? Unless you know what the four pins are I would not try it
     
  4. ejenner

    ejenner Active Member

    I had to guess which pins to use initially as there are no labels. I think this is one of those things that just have to know and it would be part of basic knowledge of components. i.e. if you know how capacitors work it would be possible to answer this question immediately without a diagram. Not meaning to put you down as I don't know the answer either.

    On the base of the capacitor there is a dividing line between one side and the other. So I determined from that it would connect the same way the original one did. The original capacitor had the same dividing line but only two pins.
     
  5. sparky steve

    sparky steve Screwfix Select

    Check the manufacturers datasheet, some of the pins may not be connected to the working part of the capacitor and only provided for mounting purposes. In addition,
    if you have a multimeter you could measure resistance between terminals.
    If parallel, you should have 2 sets of 2 connected. :)
     
  6. ejenner

    ejenner Active Member

  7. ejenner

    ejenner Active Member

    Are you saying 'if parallel' - i.e. if the pins on either side are for the same purpose... then I should use both pins on both sides?

    It's hard to tell just from the sound of the fan as I cleaned the blades and took a lot of crud off them. Like a millimetre of crud off the front and back of each blade. So just by sound alone I can't tell whether it's running at full speed. It just seems a bit anaemic to me. Could it be running at half speed if I'm only using two of the four pins?
     
  8. FlyByNight

    FlyByNight Screwfix Select

    Double pins tends to mean they are joined internally. More and more are coming like it and it means if you use one, you need to put an insultated crimp on the other as a precaution.
     
  9. ejenner

    ejenner Active Member

    I could probably check if they're joined inside with a continuity test?

    I did think there is a possibility of the secondary pins being live so tucked them out of the way and made sure they cannot contact anything.
     
  10. sparky steve

    sparky steve Screwfix Select

    On most capacitors of this type, the connections are 2 u bend connections. You use one lead to one of these u connections and one lead to the other u connection. The u bends are below a potting compound, so without testing you can’t tell which is which. Except that there is a raised line between the 2 u bend connections. This means you connect one lead to each side of this line.

    Hope i’ve explained well enough for you to understand?
     

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