I have two Sonneman LED light strips in my bathroom, each connected to its own transformer. They're controlled by a single dimmer. They have worked fine for 4 years but now when I switch them on they go off and on, off and on, and so on, continuously and simultaneously. Does this suggest a dimmer problem given that it's not one light doing this, but both, simultaneously? Also why would a dimmer go bad after 4 years?

I'll just add that - before this started happening - when the dimmer was turned all the way up, the lights blinkered, so we kept them turned down a notch.

  • 1
    What type of dimmer are you using here? 0-10V? Triac? Something else? Jun 27, 2021 at 13:49
  • do they start blinking instantly, or after they have been on a short while?
    – dandavis
    Jun 27, 2021 at 21:32
  • I'm not sure what type of dimmer it is.
    – user137797
    Jun 28, 2021 at 11:24
  • They start going on and offer immediately. It's not so much quickly blinking as just going on and off as if you were moving the dimmer up and down yourself over and over.
    – user137797
    Jun 28, 2021 at 11:27
  • in that case it's plain busted and need replaced. If it took a while, it could have been a problem with heat buildup that a cleaning could possible address.
    – dandavis
    Jun 29, 2021 at 3:13

2 Answers 2


The power supply is "crowbar"-ing

The load of the LEDs is overloading the DC power supply. It powers up, detects overcorrect, and shuts off to protect itself. Remove the overload.

Before, that was only a problem when the LEDs were at max brightness per the dimmer. You didn't fix it then, and chose to "work around it". That unresolved problem has come home to roost, as aging components in the dimmer cause it to be brighter or to be stuck "on" full.

What does this mean? Power supply is too small

You need a bigger (more amps) DC power supply.

Once that is taken care of, you may find a second problem, such as a dimmer that is stuck on full, as I alluded. If you don't really care about dimming, you don't need to dim.

  • Thanks, @harper. What do you think I should tell the electrician? Select the correct type of dimmer? Or is it a matter of the transformers?
    – user137797
    Jun 28, 2021 at 11:34
  • @MAHome Sorry, I was so quick to name the problem I forgot to say what the problem is. It's a DC power supply (not technically a transformer) and it is too small for the load. You need a bigger DC power supply. Jun 28, 2021 at 14:30
  • Many thanks for the information.
    – user137797
    Jun 29, 2021 at 22:03

I think you have a leading edge dimmer and you need a trailing edge dimmer. I suspect this because you have had the problem from the start, just not as pronounced. This can happen when the dimmer is not the correct type. You can purchase them either way or some do both. Replace the dimmer. I find it highly unusual that both "transformers" DC power supplies would fail exactly the same way and in the same time frame. Since I do not have the dimmer information get one that does both ways and try it, if it gives you problems simply set it the other way.

  • I appreciate the advice. Very kind of you all.
    – user137797
    Jun 29, 2021 at 22:04

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