If the temperature display is abnormally high when the battery is powered, the battery is dead.
If the temperature display is below zero or much lower, the circuit board temperature chip is damaged and the board should be returned to the factory or a replacement board should be issued.
Use a multimeter to measure the resistance of the temperature line against the PT100 or PT1000 temperature comparison table.
If the temperature display is always -0.0℃, it means that the temperature signal line is loose or has fallen off.
Solution:
Temporary adjustment to fixed temperature compensation
Return the circuit board to the factory or send a replacement board