Setup
| Item | Details |
|---|---|
| Hub | Aqara Hub M3 (model: [check in app]), online throughout |
| Switch | Aqara Dimmer Switch H2 US (model: [check in app]), Zigbee mode |
| Bulbs | 3 x Aqara LED Bulb T2 (E26, CCT) (model: [check in app]), Zigbee mode, firmware 0.0.0_0031 (up to date) |
| App | Aqara Home 6.4.4 (up to date) |
| Voice / UI | Apple Home and Siri, with the Aqara devices shared to Apple Home through the M3 |
| Location | US apartment, 120 V |
How it is configured:
- All three buttons on the dimmer (On/off, Brightness+, Brightness-) are in Decoupled Switch Mode, so the buttons never switch the output.
- The dimmer’s output is left on at 100% to keep the bulbs powered at all times.
- The bulbs are in an Aqara lighting set. Button presses fire Aqara automations:
- On/off: two state-based automations (WHEN Press, AND Bulb 1 Is On / Is Off, THEN lighting set off / on)
- Brightness+ and Brightness-: step automations on the lighting set
- This is the standard pattern for smart bulbs behind a smart switch, and it worked well until the events below.
History with this switch
1. Bulbs kept unpairing (“accessory deleted”). After replacing the ceiling fixture, the T2 bulbs on this dimmer dropped out of Aqara Home twice, and the M3 announced “accessory deleted” aloud. Decoupled mode was confirmed on for all three buttons.
2. Cause found: the dimmer’s on/off transition. Under the dimmer’s settings, “Transition settings of turning lights on/off” had both “Off to On” and “On to Off” dimming duration at 500 ms (as found; I did not set this). Turning the dimmer’s Switch off and back on from the Aqara app reproduced it immediately: the M3 announced “accessory deleted”.
After setting both durations to 0, I cycled the dimmer’s output off and on six times (with a long gap between cycles). All three bulbs stayed paired and controllable, and the hub stayed silent. Bulbs re-added, lighting set and automations rebuilt, everything worked again.
My reading: with a ramp, the T2 bulbs see a brief chopped or partial supply while the dimmer fades the output, and they treat it as the rapid power cycling that triggers a factory reset. I could not find this documented anywhere, so I would be glad to hear if others have seen it.
3. Apple Home and Siri can switch the dimmer’s output. Because the dimmer is shared to Apple Home as a light, Siri commands act on its output as well as on the bulbs. Decoupled mode only stops the physical buttons. The same thing happened in my kitchen (also a Dimmer Switch H2 US with T2 bulbs): after “Siri, turn off the kitchen lights”, the wall button did nothing because the dimmer’s output was off and the bulbs had no power. On my Light Switch H2 models I can use Relay Lock to stop this, but I have not found an equivalent on the Dimmer Switch H2 US.
What happened this time
- Oct 16, 18:47: Aqara Copilot reports “Oliver Bulb 1” (one of the T2 bulbs on this dimmer) went offline at this time.
- Oct 17, ~19:37: I said “Hey Siri, turn off all the lights.” Aqara Home shows the dimmer last online at 19:37 that evening. Its Switch now shows off, brightness 98%.
- Since then:
- Dimmer shows Device Offline in Aqara Home. Accessory Diagnose shows last signal strength “Excellent”.
- Apple Home shows the dimmer and bulbs as No Response.
- No indicator light on the dimmer, and pressing any button does nothing at all at the switch.
- All three bulbs are offline.
- What I have tried:
- Restarted the M3 from the app and waited several minutes. No change. Copilot confirms the hub itself is online.
- Checked the panel: no breaker appears tripped.
- Metered an outlet in the same room: 120 V. (I have not yet confirmed it is on the same circuit as the dimmer.)
- I have not yet cycled the breaker or opened the switch box.
Questions for the community
- Has anyone seen a Dimmer Switch H2 US go completely dark (no LED, no response) after its output was switched off from Apple Home or Siri? Did a breaker cycle bring it back, or did the unit fail?
- Is there a button gesture to restart the Dimmer Switch H2 US without a full factory reset? If a factory reset is the only option, what is the exact gesture for the US model?
- Is there a way to stop Apple Home / Siri from switching the dimmer’s output (an equivalent of Relay Lock on the Light Switch H2), or to share only the button events and not the light to Apple Home?
- Can anyone confirm the transition setting resetting T2 bulbs? Is 500 ms the factory default, and does Aqara recommend 0 when the dimmer feeds smart bulbs?
- For anyone running T2 bulbs behind this dimmer: did you end up replacing it with a Light Switch H2 (with Relay Lock) instead? The bulbs dim themselves, so the dimmer adds little in this setup.
Thanks in advance. Happy to post screenshots of the settings and diagnostics if useful.