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My client has a 4 bulb light fixture on a ceiling fan which was working fine but now when you screw in the fourth bulb all bulbs turn off. I believe its wired in a series. but why would it suddenly start doing this? I have tried switching the bulbs around to make sure it wasn't the fixture itself or one bulb socket and it does the same thing. works fine with 3 bulbs. when it cuts off i have too flip the wall switch on/off to get it to work again.

Dazed and confused. Any help appreciated.

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  • Check the wattage limiter in the fan. It's either faulty or being overloaded. What wattage bulbs are you installing and are they incandescent, CFL, or LEDs?
    – brhans
    Commented Jan 25, 2020 at 18:46
  • What sort of bulbs are you using, and what wattage are they? Also, what is the wattage rating on the fixture?
    – ThreePhaseEel
    Commented Jan 25, 2020 at 19:27
  • Okay. I didn't realize ceiling fans had a wattage limiter. and I'm not sure if she changed the bulbs recently, If so that makes since. I will check when I go back.Thanks
    – user111633
    Commented Jan 25, 2020 at 21:11

2 Answers 2

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This is all LED related.

Option 1: You are changing from incandescent to LEDs.

The new LEDs you are using do not play well with the dimmer, smart switch or other smart electronics currently installed. Those old electronics depend on a unique characteristic of incandescent bulbs, which most LEDs do not bother emulating. When you change the last incandescent to LED, that breaks the smart device. The fix here is to address the incompatibility (change one or the other) or add a Lutron LUT-MLC, which provides the characteristic the old dimmer/etc. is looking for.

Option 2: You are using incandescents, not LEDs.

Most fans have a safety circuit designed to prevent you from overlamping the light sockets, meaning put in bulbs that are too large and make too much heat. These would damage the fixture or start a fire.

Adding the fourth bulb pushes the power draw over the limit, resulting in the safety circuit doing its job.

The cure here is to use LED lights, which draw vastly less power, and can give plenty of light for far less heat. The fixture cares about the heat, not the light.

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Since you are not blowing any fuse I expect that that the fixture is equiped with low voltage halogen bulbs. Let us assume that the original bulbs were 10W than the power supply has to supply 40 W. If you replaced the bulbs with 15W than with 3 bulbs you reach 45W thereby not invoking the internal protection of the power supply. When you place 4 bulbs you reach 60W and the internal protection of the supply switches the lamps of.

So verify if the wattage of the bulbs is the same as the original. If more than you need to return to the lower wattage. If correct than the power supply has a problem

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  • Thanks. I am going to check that when I go back to her house.
    – user111633
    Commented Jan 25, 2020 at 21:12

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