I have a heater by Mill. It has a temp sensor inside, so it will disable heating if the desired temperature is reached. The problem is, that the heater sits on a cold wall. The room is therefore already warm enough, but the sensor inside the heater says it still needs to heat.
I have a separate temp sensor in this room. Is it possible to disable the heater if the desired temperature set in the heater is reached (but evaluated by the separate sensor - not the one inside the heater).
You could create an automation to turn off the heater when the temperature changes that checks it against the sensor, something like this (assuming your heater is a climate device called heater and your sensor is a sensor device called room_temp):
{% if float(state_attr('climate.heater', 'temperature'),0) < float(states('sensor.room_temp'), 0) %}
... code to turn off the heater such as setting the HVAC mode of the climate device or lowering the set temp, etc
{% endif %}