Dimmer won't turn off

There are 25 replies in this Thread which was already clicked 12,796 times. The last Post () by thgoebel.

  • I just got my first dimmer and installed it to some leds in my living room. The problem is that the leds will not turn off completely when I turn it off in the app or on the physical switch. It only dims down to maybe 40% and when I dim it down to 1% it's still very bright.

    Is the dimmer broken or is something else wrong?

    It's connected to 17 leds with a total of 153 watts.

    • Official Post

    Did you calibrate it?

    Maybe you have entered a value in the settings under Minimum Brightness?

    LG Michael

    Einsteigertipps / Tips for beginners

    Meine Shellys:

    In Betrieb:

    Zur Zeit über 80 Shellys, in der Regel alle Cloudverbunden

    Testboard mit fast jedem Shellygerät auf dem Markt

    Kein übergeordnete System. Nur App und WebUI mit Cloudverbindung. Sprachsteuerung mit Alexa:)

  • Seems like the Shelly Dimmer is a little bit buggy. If i turn on the lights through the app the minimum brigthness is correct, i've set it at 13% and it stays like that everytime.

    Turning on the lights through the physical wall switch then it also shows 13% in Shelly App also. But the light is incredibly lower than when turning it on through the App instead.

    Turning on the light through the Home Assistant Integration it shows the same behaviour as i would turning it on through the Physical Switch.

    Some facts: Turning it on through the Shelly App it shows 2.7w on 13% brightness. If i turn on the light through the Physical and Home Assistant it shows 2.4w on 13%

    Calibration and everything like that has been done.

    So clearly there's a software bugg

  • Hi,

    i have the same problem with my shelly dimmer. The light won't completly switch off. How can I check hardware?

    I've also done the calibration several times, but it didn't changed anything.

    BW Maximilian

  • Hi,

    I have the same problem but it appeared just during normal use.

    For me this seems like a HW defect. I suspect the power MOSFETs are gone.


    1) It appeared during normal use (using latest FW from March '20)

    2) I took out the device from the wall switch and connected it on my desk using

    - no external switch (just app-controlled)

    - a 60W incandescent light bulb as load, where dimming should not be an issue in any mode using a resistive load).

    --> Even with this minimal setup and control over the app, the light does not switch off completely (but flickers at approx. 20W usage).

    Starting with the latest Firmware (where the problem occurred), I also erased the flash and reverted to FW version 20191014-073321/master@a19acb9.

    No change, still same behavior:
    Even when apparently switched off (indication in the web-interface), the device takes approx 20W of a

    I am looking forward to the reply of shelly support team.

    Add. note: I have 2 shelly dimmer showing the same behaiour.

  • Hi,

    it seems that 1 MOSFET or its control (HW or SW) is broken.

    I had a look at the output with my scope and found that only the positive half-wave of the line (sine) is being "switched-off".

    Also during calibration, the "control" of one half-wave can be viewed. The other half wave is always on.

    So, in fact, the off-state equals 50%.

    Does anyone have the schematic of the device? I am wondering why 2 MOSFETs are being used, one for each half-wave...

    • Official Post

    The schematic has only the developer.

  • Hi,

    Looking at the latest make magazine, by using different schematic, shelly could even spare one of the two N-channel mosfets and spend the money saved into a more reliable one from ST, onsemi or any other supplier other than Oriental Semiconducter.

    Mabe that would improve the device and hereby customer satisfaction.

    P.S. It is definitively one of the MOSFETs which is broken in two of my shellys (same in both). The MOSFET has a nice shortcut from source to drain.

    • Official Post

    Write a mail to the support or open a ticket.

    Perhaps, they do so.;)

  • Hi,

    I already created a ticket 4 days ago. I am keen to see what they will answer. So far I received only an automated answer. Maybe they are also in some shutdown mode.

    In worst case (if they won't offer device replacement) I'll order an Onsemi MOSET at Farnell and replace the broken part myself.

    In case anyone else is interested, we could discuss which part is the most suitable one.

    Best Regards


  • Hi,

    It seems that I have the same problem on a shelly dimmer. When I did the installation and the test everything seemed ok. Then I pushed everything into the box and the problem appeared.

    Rainer have you heard from Shelly support?

  • Hello everyone,

    The same problem was.

    I tried to downgrade the firmware, using the beta version, reset the same, always the same result.

    But it can dim the lights, but it never goes off!

    • Official Post



    When I did the installation and the test everything seemed ok. Then I pushed everything into the box and the problem appeared.

    I don't think, that this is a problem of the Shelly. I think you don't have enough place in your box.

    Can you post a picture, please?

  • Hello Rainerlan,

    Did you ever get a response? I am having the exact same issue, only powering down to ~50% and just curious if this unit is junk now. Thanks in advance.

  • Hello Rainerlan,

    Did you receive any update from the support team? I likely ran into the same problem described in this thread (I used Shelly Dimmer 2 connected to a light without the neutral line). When I connect the SD2 to the light, it always stays turned on at around 40% while the application still says that it is turned off (even after multiple factory resets, calibrations, reboots). If I try to turn on the light through the app and to increase the brightness to more than around 70%, the light starts flickering. I suspected this problem had been a hardware issue, and according to what I read in this thread I'm more convinced about it...


  • Hello Rainer,

    in April you've posted that:

    have you got any answer from Shelly support till than? I've the same problem here: during normal operation two Shelly dimmer decided to keep the lights on when turned of - some weeks ago the first one, on the weekend the seond.

    As I can clearly see here that I'm not the only one and it seems to be a general issue, I'm interested to know what is Shelly's position about it - if they accept to have that problem and replace the affected units or if they are blaming the owners of mishandling or something.

    Anyway, I'll create a ticket today and find out myself.

    Kind regards,


  • I have exactly the same problem. I installed (with neutral wire attached), calibrated and flashed updated firmware. After that it worked correctly for one week on driving a dimable LED bulb. It was disconnected from power briefly yesterday and hasn't worked correctly since. When off, the light appears to be on at about 50%. When on dimming appears to range from 50% to 100% only. At 50% there is visible high frequency flickering consistent with a half-wave at 50 Hz.