ComfoClime-App unresponsive (grey screen) & bogus values

[helgeklein]

I don't think this problem is related to the HA integration but I hope someone can give me a hint on how to solve this.

I noticed that Zehnder's ComfoClime app doesn't work anymore. The initial screen ("Wohnungsauswahl") shows my device as green but when I tap it I only get a grey screen and the app hangs.

When I query the dashboard API I get some correct but also some bogus values:

# Command:
curl $IP_ADDRESS/system/$UUID/dashboard

# Response:
{"indoorTemperature":24.9,"outdoorTemperature":23.6,"exhaustAirFlow":405,"supplyAirFlow":418,"fanSpeed":2,"setPointTemperature":6553.5,"season":236,"schedule":0,"status":255,"heatPumpStatus":0,"hpStandby":true,"freeCoolingEnabled":true,"caqFreeCoolingAvailable":true}

Note the following:

• setPointTemperature: 6553.5
• season: 236
• status: 255

Resetting the ComfoClime's Arduino board via the tiny reset button didn't change anything, neither did a full power cycle of both the ComfoAirQ and the ComfoClime.

Any ideas what might be going on?

[helgeklein]

Some more observations:

The ComfoClime is responsive via the API. Most returned values look good to me.

Changing values via the integration has no effect.

The ping and health APIs return the following:

$ curl $IP_ADDRESS/monitoring/ping
{
  "uuid": "MBE123123123",
  "up_time_seconds": 1614,
  "timestamp": "2025-09-07T13:55:41.0Z"
}

$ curl $IP_ADDRESS/monitoring/health
{
  "total_free_bytes": 102192,
  "total_allocated_bytes": 127740,
  "largest_free_block": 41984,
  "minimum_free_bytes": 39060,
  "allocated_blocks": 526,
  "free_blocks": 63,
  "total_blocks": 589,
  "up_time_seconds": 1624,
  "twai_msgs_to_tx": 0,
  "twai_msgs_to_rx": 0,
  "twai_tx_error_counter": 0,
  "twai_rx_error_counter": 0,
  "twai_tx_failed_count": 0,
  "twai_rx_missed_count": 0,
  "twai_rx_overrun_count": 0,
  "twai_arb_lost_count": 169,
  "twai_bus_error_count": 0,
  "open_sockets": [
    58
  ]
}

[helgeklein]

Factory resetting the ComfoClime's Arduino board as described in the installation manual is not possible. As described in the manual, I first pressed the reset button and then (while still pressing the reset button) also pressed the restore button for more than 10 seconds. Different from the manual's description, the green LED does NOT start blinking.

When releasing the buttons, the Arduino reboots but keeps its settings (including the WiFi configuration). The only change I noticed is that, apparently, the provisioning mode is enabled:

$ curl $IP_ADDRESSS/wifi/list
{"provisioning":1,"ble_id":"12:34:56:78:90:12","current":"WIFI_NAME","connected":true,"wifi":...

[helgeklein]

The various APIs that return a list of devices only list the ComfoAirQ now. The ComfoClime is missing. An example of this is the /system/$UUID$/devices API endpoint.

Similarly, querying the serial number of the ComfoAirQ via /device/$UUID/property/1/1/4 works, but the same call with the UUID of the ComfoClime only returns Serial number not found.

[msfuture]

That's strange. Did that happen suddenly or after a firmware update?
Can you query the /system/$UUID/alarms endpoint?

[helgeklein]

Very strange indeed. I haven't changed anything in the last 1-2 weeks. It "just happened".

The alarms endpoint also lists only the ComfoAirQ device:

{"devices":[{"uuid":"SIT123123123","modelTypeId":1,"variant":3,"zoneId":1,"errors":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]}]}

A few months ago when I documented it that was different.

[helgeklein]

This is what the Arduino board looks like in case someone notices anything:

[msfuture]

Looks quite normal in comparison to mine (except my rotary switch is on 1, as I have the ComfoClime 24).
You could try to disconnect the ComfoNet Bus an powercycle the Clime unit. Maybe there is a bus error somewhere, that causes the communication issues. The clime unit should then issue an error, that it couldn't find the ventilation unit.
It's strange that the reset isn't working. I used the factory reset some time ago after some changes in my network environment without any problems.

[helgeklein]

No change, unfortunately. I'm thinking that there must be an issue not with the Arduino board, as that is responding to API requests, but instead with another internal system.

[tokylo]

Do you have any other gateways connected to the Q450? I have an IP gateway, a KNX gateway, and the CC connected to the ComfoBus at the same time. After a power outage, I have trouble getting all three gateways back online. Then I have to unplug and reconnect the KNX gateway.

[helgeklein]

No other devices. In the past I did have first a KNX and and later an IP gateway connected, but I've removed them months ago.

[helgeklein]

I opened the ComfoClime unit. In the upper-right corner there is a board with an LED. When I power on only the ComfoClime, that LED blinks red in a weird pattern (note: ComfoAirQ powered off to prevent ventilation air blasting through the open ComfoClime). No idea if that's an indication of a problem, though.

[helgeklein]

Fixed it!

I obtained the correct procedure to perform a factory reset from Zehnder Support (hint: not the way it's described in the manual). That did it.

To help the next guy perform a factory reset I documented the correct procedure here.