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Wiring & switching Shelly troubleshooting

Shelly turns on by itself after a power cut

The power comes back and so does the light, even though you'd turned it off. It's usually the power-on setting, and it takes a minute to change.

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  • Gen4
  • Gen3
  • Gen2

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What are you seeing?

Pick the closest match and we'll point you to the fix most likely to sort it.

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Why it happens

When the power comes back, a Shelly relay doesn't remember on its own what you wanted. It does what its power-on setting tells it to: turn on, turn off, go back to the state it was in before the cut, or follow a flip switch on the wall.

If that setting doesn't match how you use the light, it'll come on, or stay off, after every blackout. A timer or a script that runs on startup can do the same thing, a few seconds or minutes later.

Before you start

Every fix here is a setting in the Shelly app or the device's web page. Don't open the wall plate. If the device is warm, buzzing or clicking on its own, turn it off at the switchboard and call a licensed electrician.

Quick checks first

Run these checks before moving on to the fixes.

Checklist 0 of 2 checked
Look at the wall switch

If the light is wired to a flip switch, note whether it's up or down. If it's in the on position, the device may be following it.

Check the Timers tab

Open the device in the app and look at its Timer tab. An Auto on timer turns it back on a set time after it turns off.

Fixes, most likely first

Work down the list and stop when it's fixed.

  1. The power-on setting is wrong for you

    How to tell. It does the same thing after every power cut: always on, or always off, whatever state it was in before.
    • Open the power-on setting on its web page

      Open the device's IP address in a browser, open the output's settings and go to Input/output settings. Find Action on power on.

    • Pick the behaviour you want

      Choose Turn OFF to keep it off after a blackout, or Restore last known state of output/relay to put it back how it was before the power went. Then click Save.

    • Or change it in the app

      In the Shelly app, open the device's Settings, then Input/output setting, and change Set relay power on default.

  2. It's set to follow the wall switch

    How to tell. It's wired to a flip switch, and after a cut it always matches the switch position, not what you last set in the app.
    • Check the power-on option

      In Action on power on, the option Current state of the switch (shown as Match input in some app versions) makes the output follow the wall switch when the power returns.

    • Choose another option

      Pick Restore last known state of output/relay if you want it back how you left it, or Turn OFF if you'd rather it stays off until someone turns it on.

  3. An Auto on timer is switching it back on

    How to tell. It's off when the power returns, then comes on by itself a set time later, and does the same after you turn it off normally.
    • Turn off Auto on

      On the device's web page, open the output's settings and go to Timers. Under Auto ON, untick Enable and click Save. In the app it's the Timer tab. Leave Auto off alone if you use it.

  4. A script runs when it starts

    How to tell. The device runs scripts, and the output changes a few seconds after it boots up.
    • Check which scripts run on startup

      Open the device's web page and go to Scripts. The toggle beside each script runs it on startup. Turn it off for any script that switches the output and shouldn't run after a blackout.

  5. A schedule fell inside the blackout

    How to tell. You have a schedule that should have switched it while the power was out, and the next scheduled time works normally.
    • Know what Shelly does after a cut

      When the power returns, the relay follows its power-on setting. A scheduled event that fell inside the cut doesn't run afterwards, and the next one runs as normal.

    • Set the power-on setting to suit the schedule

      If you'd rather it's off after any blackout, whatever the schedule says, set Action on power on to Turn OFF.

    • Make sure it can get the time

      Schedules need a working internet connection so the device can sync its clock. If the router takes longer than the device to come back after a cut, the device can't check the time until the internet is back.

Frequently asked questions

No. A scheduled event that falls inside the power cut doesn't run once the power returns. The next scheduled event runs as normal.

Yes. Set the input to Detached in Input/output settings, and the switch no longer changes the output. You then control it only from the app, schedules or scripts.

Turn ON, Turn OFF and Restore last work with any switch. Current state of the switch only works with a flip (toggle) switch.

Scripts that help

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