Generally, 5K--10K is used for hanging machines, and 10K---20K is used for cabinets. Specifically, you need to use your own multimeter to measure the resistance.

The general ambient temperature sensor is a small thing that is close to the fins in the black side of the outdoor unit against the wall. The temperature sense of the tube is inserted in the wall of the coil inside the outdoor unit.

The copper head is used to detect copper tubes, and the temperature is fast. The plastic head is generally used to detect ambient temperature, corrosion resistance and high reliability.

 

 

The air-conditioning circuit designer uses the normal temperature of 25 degrees as the reference, that is, when it is 25%, RTl=R1, RT2=R2, and the voltages of points A and B are 2.5V. Some circuits are equipped with R3 and R4, which mainly serve as a buffer. When the ambient temperature rises, the RTI resistance decreases, the voltage at point A rises, the comparator outputs a differential pressure, and a series of internal processing of the CPU controls the internal and external operating states.

Large air conditioner, inverter air conditioner external control board, temperature sensor connected VI sampling voltage is not 2.5V, but 1/4 power supply voltage, which is 1.25V, in fact, there is a method to determine the thermistor resistance is particularly simple, Choose a 50k potentiometer and a thermistor universal plug. For convenience, you can connect with long wires. Unplug the suspected thermistor, plug in the universal plug, energize the air conditioner, and test the potentiometer with the multimeter 5v. The voltage of the terminal slowly turns the potentiometer handle. When the voltage is 2.5V, the rotation stops. At this time, the resistance of the potentiometer is the resistance of the thermistor. For example, if the resistance is 8k and the ambient temperature is about 30°C, then the temperature sensor has a resistance of 10k.

 

 

If the air conditioner temperature sensor is broken, the following phenomena will occur, and the air conditioner temperature sensor can be judged by this:

1. The indoor ring temperature sensor has a large resistance value, causing the air conditioner to start frequently.

2. The resistance of the indoor tube temperature sensor becomes smaller, which causes the whole machine to be protected soon after starting.

3. The indoor temperature and temperature of the pipe are changed, causing the air conditioner to malfunction.

4. The indoor tube temperature change value is 0 Ω, which causes the whole machine to start remotely without reaction.

 

 

The temperature sensor barrier has a relatively large proportion in air conditioning faults. To accurately determine the function, the air conditioning control section has three temperature sensors:

1. Room temperature sensor: mainly detects the indoor temperature. When the indoor temperature reaches the set requirement, the internal and external machines are controlled. When the cooling is stopped, the external machine stops, and the internal machine continues to run.

2. Indoor tube temperature sensor: It mainly detects the coil temperature of the indoor evaporator, and prevents cold air, anti-overheat protection and temperature automatic control during heating.

3. Outdoor defrosting temperature sensor: mainly detects the outdoor condenser coil temperature. When the outdoor coil temperature is lower than -6 degrees Celsius for 2 minutes, the internal machine turns into a defrosting state, when the outdoor coil sensor resistance is too large The indoor unit does not work properly.

 

 

1. The remote control setting is incorrect;

2. The filter is not cleaned in time;

3. There are items in the air inlet and outlet of the air conditioner that affect the heating effect. The room has a heat source or many indoor personnel, resulting in poor cooling effect;

4. The room insulation effect is poor;

5. The indoor power supply voltage is too low, resulting in low efficiency of air conditioning;

6. The ambient temperature is too high or too low, resulting in poor results.

During the air conditioning maintenance process, the temperature sensor (thermistor) has a high proportion of faults. If there is a fault such as open circuit, short circuit or poor characteristic curve, the air conditioner will display an abnormal code and cannot work normally. Since the temperature sensor does not indicate the parameters and resistance values, it is often difficult to determine during maintenance. It is the same brand and different models, and the resistance values ​​are not necessarily the same.

The temperature sensor, that is, the resistance decreases as the temperature rises; the resistance increases as the temperature decreases.

The negative terminal sampling voltage of the CPU comparator is 1/2 of the CPU power supply voltage, which is 2.5V.

The peripheral circuits RT1 and RT2 have pull-up resistors on the positive side of the comparator, and R1 and R2 are the lower bias resistors.