LED aquarium light (a bar with many small bulbs) with manual switch built into cord; Customer requested automatic timer. Placed automatic timer between LED's plug & wall outlet. Functioned well for 2 months. Now, when the timer clicks to ON, the LED won't light fully: one end of the LED light's bar glows, but the rest is dark. BUT...

If I switch the built-into-cord switch off & on, the LED lights up! ??

If I remove the timer, the in-line switch & light function normally.

I plugged an incandescent light into the timer and the timer functions normally.

Any ideas?

  • Hello, and welcome to Home Improvement. I'll guess that this is an electronic timer; there's likely something about how it turns on that's causing the problem. And, big props for taking our tour before posting; most newbies don't bother. Commented Oct 21, 2019 at 10:22
  • The timer is mechanical; a circular rotating base with an outer ring of little tabs (1 for each 15 minutes) that, when manually placed, the "up" position cuts the current and the "down" position turns it on... Commented Oct 21, 2019 at 10:31
  • Note that, when the timer is supposed to allow current, (tab down), the tiny LED bulbs at one end of the light bar glow dimly; the current is reaching the light. The strange thing is that when I use the in-cord simple switch (between the timer and th light bar) to manually cut the current and then re-connect, the LED bar lights up fully as it should... Commented Oct 21, 2019 at 10:36
  • I could guess but instead let me ask a question instead. Is this light assembly some very cheap non-recognized brand purchased from an online retailer?
    – Michael Karas
    Commented Oct 21, 2019 at 11:39
  • No, the light fixture and in-line manual switch is part of a complete aquarium purchased in an aquarium & tropical fish store; replacing just the light fixture would cost over $100. The automatic timer/switch was purchased separately. Commented Oct 21, 2019 at 11:49

1 Answer 1


Into the trash it goes

The timer is almost certainly malfunctioning and not providing "clean" voltage & current to the lighting.

This surely has something to do with "leakage current" as we often see with devices working fine with incandescent and then choking on LED. However there's no reason for a timer to be built that way. Further, the fact that it started doing this now proves it's some sort of electronic degradation.

Look at the timer; if "CE" (Chinese Excrement) is the most prominent listing agency mark, then waste no further time on it. Amazon Marketplace, eBay or Aliwhatever are not reliable sources for quality parts.

  • Thanks! Good call. Already bought a new one, timer & light are working as they should. Commented Oct 21, 2019 at 23:01

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