The indoor pipe temperature sensor, also known as the indoor coil temperature sensor, primarily measures the temperature of the indoor evaporator coils. It has two main control functions:
1. During system heating, it provides protection against cold air, overheating, and automatic temperature control. When the system is first turned on, if the coil temperature hasn't reached 25°C, the indoor fan will not run. When the temperature reaches between 25°C and 38°C, the indoor fan runs at a low speed. When the temperature exceeds 38°C, the fan operates at the set speed. If the indoor coil temperature reaches 57°C and persists for 10 seconds, the outdoor fan stops running. If the temperature exceeds 62°C and persists for 10 seconds, the compressor also stops running. Therefore, when the resistance value of the pipe temperature sensor is larger than normal, the indoor unit cannot start or continues to run at a low wind speed; when the resistance value is smaller than normal, the outdoor unit frequently stops, and the indoor unit blows cool air.
2. During system cooling, it provides freeze protection. If the indoor coil temperature falls below -2°C continuously for 2 minutes, the outdoor unit stops running. When the indoor pipe temperature rises to 7°C, or the compressor has been off for more than 6 minutes, the outdoor unit resumes operation. Therefore, when the resistance value of the coil temperature sensor is too large, the outdoor unit stops working, the indoor unit blows natural wind, and a no-cooling fault occurs. The defrost temperature sensor, also known as the outdoor coil temperature sensor, primarily measures the temperature of the outdoor condenser coil. When the outdoor coil temperature drops below -6°C and persists for 2 minutes, the indoor unit switches to the defrost state. If the defrost temperature sensor's resistance value is too high, the indoor unit cannot function properly.
Haier Air Conditioner Repair Q&A: The Function of the Indoor Pipe Temperature Sensor
Beijing Haier Air Conditioner After-sales Service Center, edited and organized on September 23, 2011.