When the air conditioner cannot operate normally, in addition to checking the starting relay, overheating, overcurrent protector and capacitor of the compressor, it is also necessary to check the main control selection switch of the air conditioner thermostat, which is a very important control protection and actuator component in the electrical control system. Here are a few common methods for rapid detection of air conditioner thermostats.
1. Bellows or diaphragm air conditioner thermostat
1. Fault phenomenon: poor contact or incineration, forming a circuit that cannot be connected; The contacts frequently act and arc adhesion, forming a circuit that cannot be broken; The thermostat in the temperature sensing cavity leaks, forming a contact that cannot be operated and loses its control function.
Maintenance method: After rolling the knob of the air conditioner thermostat in the forward and opposite directions several times, use the multimeter R×l gear to measure the two terminals of the temperature controller on condition, if the resistance value is very small, indicate that the contact is normal; If the resistance is very large, it indicates that the contact contact is poor; If it doesn't work, it may be that the temperature sensor is leaking.
Whether there is leakage can be first visually inspected, observe whether the sealing welding head of the temperature sensor head is cracked, whether the temperature sensor package is damaged and cracked, whether the temperature sensor tube has bending marks, etc., and then put the temperature sensor package in warm water of 30-40-C to test whether the contact is closed, if the contact is still not closed. Indicate that the temperature sensor in the temperature sensor package has been leaked; If the contact can be closed, then take out the temperature sensing bag from the water, and then the contact is disconnected after being placed in a low temperature environment for a period of time, indicating that the temperature control scale of the thermostat is improper, it can be corrected by adjusting the temperature scale of the adjusting screw, roll L in the counterclockwise direction, and try again after 2 hiding.
2. Fault phenomenon: after the contact of the air conditioner thermostat is adhered due to ignition. The contacts cannot jump open automatically, and the compressor cannot be stopped.
Maintenance method: Put the temperature sensor bag in the cold room (5-lO°C) of the double-door refrigerator, and measure whether the two-wire terminals of the temperature controller are disconnected. If you don't keep opening. Indicate that the contact is adhered and can be mechanically forced to disconnect by turning the flat screwdriver; If the contact can be jumped open, the temperature control scale of the thermostat in the table H month drifts and is low, and the temperature control scale adjustment screw can be adjusted clockwise.
3. Fault phenomenon: leakage of temperature sensitizer
Maintenance method: heat the temperature sensor tube with a hot towel, adjust the knob to the lowest temperature, and measure whether the switch of the thermostat is turned on with a multimeter. If the switch doesn't work. It indicates that the thermostat has leaked, and the thermostat should be replaced with a new one.
2. Thermostat for hot and cold air conditioners
The thermostat used in the electric air conditioner has two sets of contact mechanisms (cold contacts and hot contacts) in the contact control box, and the same temperature sensing bellows is used to control the cold and heat. Its faults and inspection methods are fundamentally the same as those of ordinary thermostats, but it should be noted that it is also necessary to check whether the cold and hot switching actions are sensitive, that is, the compressor circuit should be connected when the refrigeration direction is connected, and the electric heater circuit should be connected when the heating direction is connected.
3. Defrost air conditioner thermostat
The defrost temperature controller is an element installed in the control circuit of a thermal air conditioner specifically for switching the solenoid directional valve.
Its thermostat is placed on the coil of the heat exchanger on the outdoor side. When heating in winter, the frost layer of the outdoor side heat exchanger thickens so that the temperature is lower than a certain set value. Contact action of the defrost manipulator.
Disconnect the solenoid directional valve. The original heating cycle is changed to a cooling cycle. There are two commonly used structural forms: one is the thermal bimetal sheet type: the other is the ordinary thermostat.
The method of detection is to place the temperature sensing part in the water or air at the corresponding temperature. Use a multimeter to measure whether the two terminals are disconnected or on. You can know the good and the bad. The thermal bimetal thermostat is also used for indoor side control to prevent cool breezes.
Fourth, temperature sensing resistance
Electronic air-conditioning thermostats or microcomputer-controlled air-conditioners use thermistors as the temperature sensing element.
A thermistor is a component whose resistance value changes significantly with the change of temperature. Thermistor for ten vertical measurement of return air temperature of air conditioner. It generally has a negative temperature coefficient characteristic: the resistance value decreases with the addition of temperature.
Details to a certain brand of abyss apparatus used in the thermistor, its resistance value changes with temperature characteristics are generally drawn in the random description book into a chart for detection, detection can be in a certain environment. Measured with semiconductor thermometers and multimeters.
When the thermistor is aging and the performance drift, that is, the correspondence between temperature and resistance value changes, a new thermistor sensor should be replaced.
Defects can occur after abnormal system operation or long-term aging. In the repair process, the replacement method is sometimes adopted, that is, replaced with an outstanding thermostat of the same model and standard, which not only saves repair time, but also can easily identify the quality of the original thermostat.
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