By Andrew · Tested in the HovelHack farmhouse
On July 25 at 12:17 a.m., 14 of our 31 smart lights dropped off Home Assistant at the same time. Not randomly, either: entire rooms went, including two bedrooms, the laundry, the dining room couch lamps, and a pair of bedroom lamps.
Clue 1: whole rooms, not random bulbs
When single bulbs flake out, you’ve got a bad bulb. When whole rooms vanish together, the problem is the path to those rooms. Either a Zigbee router in between died, or something cut power to a group of devices, like a wall switch or a breaker.
Clue 2: the error log
Home Assistant’s log was full of MAC_NO_ACK, which basically means “I sent a message and nobody answered.” The pantry automation alone threw it 141 times. That’s a radio-level failure: messages weren’t reaching the devices at all.
Clue 3: what our mesh was made of
Our lights at the time:
- 23 Sengled bulbs, which don’t repeat signal
- 7 ThirdReality bulbs, which do, but only while their wall switch is on
- 2 ThirdReality plugs, also routers
- One USB coordinator in the dining room
So the far rooms depended on a handful of routers, some of which sit behind wall switches people flip. Lose one or two of those and every end device behind them goes dark.
The fix list
- Add always-on routers. Smart plugs are the cheapest way to do it. One per far room helps.
- Keep router bulbs on switches nobody touches, or replace those switches with smart ones.
- Get the coordinator on a USB extension cable, away from the computer and the Wi-Fi router. USB 3 ports and 2.4 GHz Wi-Fi both interfere with Zigbee.
- Re-pair the stragglers after the routers are in, so they pick new parents.
The two-different-problems trap
The same week, our outdoor plugs also went unavailable. That looked like the same outage, but it wasn’t. Those were cloud Wi-Fi plugs hitting rate limits, so no Zigbee fix would have touched them. When several things break at once, check whether they even share a radio before you start fixing.