I'm looking for a good answer for an issue I'm having with some new LED light bulbs I got today. When I plug both 17w (150w equivelent) bulbs into the sockets in my garage they don't turn on at all. When I unplug one of the LED bulbs and turn on the other it won't light up either. However when I put one LED bulb in one socket and one incandescent bulb in the other socket both turn on the LED is perfect but the incandescent bulb only turns the coil in the bulb to a glowing orange. enter image description here

  • What make and model are these bulbs, and are they controlled by a regular switch or by some sort of dimmer or "smart" switch? Jan 18, 2018 at 23:18
  • They are lohas LED bulbs. They don't have a model number on them but I put a picture with the specs for them. There's no dimmer just the basic overhead screw in plate in most garages Jan 18, 2018 at 23:21
  • So, a pull-chain controlled fixture then? Jan 18, 2018 at 23:25
  • Sorry for the confusing way I worded that. It's a regular wall switch. Jan 18, 2018 at 23:27
  • if you install just the one incandescent does it work normal?
    – agentp
    Jan 19, 2018 at 0:38

1 Answer 1


The sockets are wired in series. For all I know, they always have been.

You can get away with it with incandescents, at a bit over 1/4 the light from each bulb, so a 150 looks like a 40.

With one incandescent and one LED, the LED limits current to about 130ma, which is not enough for a 150W incandescent to get up to power. As such, the incandescent doesn't see much current, and so can't drop much voltage. Therefore the LED sees near full voltage, and is able to function properly.

If you want to test the "series" theory, try installing a 150W incandescent in one socket, and a 25W incandescent in the other. If the 25 is much brighter than the 150, that confirms it.

Series is not a proper way to wire lights. The person who wired it doesn't know what they're doing. Have someone competent fix this and check all their other work.

  • 2
    Also, series is a bad idea even ignoring safety, standards, and LED compatibility: under-driven incandescent bulbs are less efficient, producing more heat relative to the amount of light (because the temperature of the filament is lower) than using a lower-wattage bulb.
    – Kevin Reid
    Jan 19, 2018 at 2:33
  • that was my thought, but see his response to my comment question. With series wiring a single bulb would not work at all.
    – agentp
    Jan 19, 2018 at 12:56
  • @agentp I saw that but the way he answered I'm not sure he understoodl your question. Jan 19, 2018 at 16:33
  • brilliant deduction. Hat's off to Harper! I'm wondering if the bulbs were like that to reduce motor vibration's effects on the filaments; cooler metal is stronger metal. anyway, amazing work.
    – dandavis
    Jan 19, 2018 at 20:03

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