Recently I tried replacing a fluorescent bulb in my garage after it failed, upon fitting the new light it wouldn't turn on and there is this knob on the side (I have been told it may be something to do with start-up or a choke or something) and I tried pushing that in / turning it but nothing happened - I now realise I perhaps should not have pushed it in but I was just wondering what it actually is? Below is an image of what I am talking about (not my actual light)

enter image description here

While this question is about what this knob is I would also greatly appreciate it if anyone could give any tips into how to get a fluorescent light to work again.
Could I have pushed the component out when I pushed the know and that is why it is no longer working? Or could it be something different all together. I briefly managed to get it back working again the other day but I honestly have no idea what it was that I did...

It is quite inconvenient this not working so I would really like to fix it but I am not an expert or even an amateur when it comes to this light. I am however an electronic engineer student so know my way around a circuit or two so am more than confident in taking it apart and replacing anything - I just don't know what I would need to replace!

1 Answer 1


That component is called the starter. its a really inexpensive component that regulary fails on florescent lights. to remove you turn 1/4 rotations left and pull out. to check that its in turn right until it stops whilst pressing.

enter image description here

Any good lighting store will have replacement starters for your light.

Otherwise the things to check would be.

  • check that the florescent is clicked in correctly, you will see that if the pins of the tube arent touching the contacts in the fitting it will not turn on. i.e. you need to rotate the tube so that the gold pins at the end of the tube sit horizontal with the ceiling.
  • check if there is corrosion on the pins of the tube
  • remove the tube (turn off light switch), then remove the backing plate look inside for wires that have been detached. the chinese lights I know have really weak connectors and the connectors are always failing
  • 1
    ...no, it's called a starter. And it's not a capacitor, or at least not "just" a capacitor. home.howstuffworks.com/fluorescent-lamp4.htm
    – Ecnerwal
    Feb 27, 2015 at 14:30
  • sorry, you are correct, its a starting capacitor, but I should have just said capacitor. the condenser portion is to remove that old hum that used to be associated with these lights.
    – Hightower
    Feb 27, 2015 at 16:31

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