Home assistant error: The unit of measurement C is not valid together with device class temperature

[niklerus]

Describe the bug
HA gives a warning about wrong unit for temperature:
"The unit of measurement C is not valid together with device class temperature, this will stop working in HA Core 2025.7.0"

To Reproduce
Steps to reproduce the behavior:
Run AMS reader v2.4.7 on ESP32 chip and mqtt.sensor logs in HA

Expected behavior
Valid temperature unit sent from AMS

Screenshots
If applicable, add screenshots to help explain your problem.

Hardware information:

• Country: Sweden
• Meter: Sagemcom T211
• Encryption enabled no
• AMS reader: ESP32
• M-bus adapter (if applicable):

Relevant firmware information:

• Version: 2.4.7
• MQTT: yes
• MQTT payload type: home-assistant
• HAN GPIO: GPIO3
• HAN baud and parity: 115200 8N1
• Temperature sensors: none
• ENTSO-E API enabled: no

Additional context
I have no temperature sensor installed.
Seems HA is expecting "°C" instead of "C".

[gskjold]

This is weird, because °C is what we have in the code:

amsreader-firmware/lib/HomeAssistantMqttHandler/include/HomeAssistantStatic.h

Line 126 in bcb3c3b

const HomeAssistantSensor TemperatureSensor PROGMEM = {"Temperature sensor %s", "/temperatures", "temperatures['%s']", 900, "°C", "temperature", "measurement"};

But maybe there is something weird going on when you don't have sensors, I will look into it