Are you familiar with the detection and maintenance methods of air conditioner components?

2024-12-22

Fuse Tube

The fuse tube is represented by FC1.2 (FUSE) on the computer board and is mainly used for over-current protection.
Fault Phenomenon: The whole machine has no power and doesn't work.
Detection Method:
Visually check whether the fuse is blown. If so, it should be replaced.
Precautions:
If only the fuse tube on the computer board is damaged and the inner wall of the fuse tube is blackened, it may be related to the short circuit of the internal and external motor windings, transformer windings, four-way valve coil, and solenoid valve coil faults. Do not blindly replace the fuse tube. Be sure to confirm the quality of the motor before replacement. For the fuse tube blown due to excessive voltage and current, only the fuse is blown from the appearance and there will be no blackening phenomenon. In addition, for small split air conditioners, there are only two components, varistor and fuse tube, on the indoor unit computer board, and there are three sets of these components on the internal and external computer boards of the one-to-two air conditioner respectively.

Power Module

The function of the power module is to convert the DC voltage input into the module into a three-phase AC power source for driving the compressor through the switching action of the IGBT inside it. The operating frequency of the inverter compressor is completely controlled by the level of the working voltage output by the power module. The higher the voltage output by the power module, the higher the operating frequency and output power of the compressor. Conversely, the operating frequency and output power of the compressor are lower.
Fault Phenomenon: The whole machine doesn't work and reports a communication fault.
Detection Method:
(1) Use a multimeter to measure the DC voltage at both ends of P and N. Under normal circumstances, it is about 310V, and the output AC voltage (U, V, W) is generally not higher than 200V. If there is no 310V DC voltage at the input end of the power module, it indicates that there is a problem with the rectifier and filter circuit of the machine and has nothing to do with the power module. If there is a 310V DC input but no AC output lower than 200V or the voltages output among the three phases of U, V, and W are not equal, it can be judged that the power module is faulty and should be replaced.
(2) In the case of not being connected to the machine, use the red test lead of the multimeter to touch the P terminal and the black test lead to touch the U, V, and W terminals. The forward resistances should be the same. If the resistance of any one item is not equal to the other two items, it can be judged that the power module is damaged. Use the black test lead to touch the N terminal and the red test lead to touch the U, V, and W terminals respectively. The resistance of each item should also be equal. If not, it can also be judged that the power module is damaged and should be replaced.
(3) Use a multimeter to measure the forward resistance of the P terminal to the U, V, and W terminals, which should be about 500 ohms, and the reverse resistance should be infinite. Use a multimeter to measure the forward resistance of the N terminal to the U, V, and W terminals, which should be about 500 ohms, and the reverse resistance should be infinite. Otherwise, it is judged that the power module is damaged and should be replaced.
(4) When determining the quality of the power module, also check the compressor and the drive power supply.
Precautions:
When replacing the power module, do not bring the new module close to magnetic or electrostatic objects, especially the sockets of signal terminals. Otherwise, it is very easy to cause internal breakdown of the module and make it unusable. And it is necessary to apply silica gel on the heat sink of the power module to ensure that the fixing screws are tightened well, which is beneficial to heat dissipation.

Photocoupler

The representative symbol is TLP. It uses photoelectric output pulse to process signals and is used to control the line signal transmission between the main board of the indoor unit and the main board of the outdoor unit of the air conditioner. The commonly used models are TLP521, TLP421 (for signal reception) and TLP371 (for signal transmission).
Fault Phenomenon: The air conditioner reports a communication fault.
Detection Method:
Use a multimeter to select a range of R*1K ohm and measure the resistance value of pins 1 and 2 as 1K ohm, and the resistance value of pins 3 and 4 as infinite. Otherwise, the component is damaged.

Over-current (Over-heat) Protector

The over-current (over-heat) protector is tightly pressed on the outer casing of the compressor (for compressors used in the early stage) and is connected in series with the compressor circuit. It can sense the current of the outer casing of the compressor and the motor. Whichever exceeds the specified value will cause the contacts of the relay to open and make the compressor stop running. Its heating elements are bimetallic strips and heating wires. At the same time, when the heating wire of the relay cools down, the bimetallic strip returns to its original shape and makes the contacts close. In addition, there is also an embedded thermal protection relay. This component is embedded in the internal winding of the compressor and directly senses the change of the compressor winding. The principle is the same as above, but it is mainly used in household air conditioners and compressors used in models such as Mitsubishi Heavy Industries Haier 306, 506, 307, and 507.
Fault Phenomenon: The compressor doesn't work after working for a period of time.
Detection Method:
Use the R×1 or R×10 terminal of the multimeter to measure the resistance value at both ends of the thermal protector. Under normal conditions, it should be zero. Otherwise, it is damaged and needs to be replaced.

Relay

The relay is represented by RL on the computer board and controls the start and stop of components such as the compressor, motor, four-way valve coil, and electric heating, and whether there is an operation signal depends on this component.
Fault Phenomenon: The compressor doesn't work; the outdoor fan doesn't work; the four-way valve and solenoid valve are not powered on; the indoor fan doesn't work or can't adjust the speed (for cabinet air conditioners).
Common Faults and Detection Methods:
(1) No pull-in: For fixed-frequency air conditioners, it will cause the compressor not to operate, but other components of the outdoor unit operate normally. For inverter air conditioners, it will cause the outdoor unit not to work.
(2) Sticking: For fixed-frequency air conditioners, it will cause the compressor to operate when powered on, and other components are normal.
(1) Use the ohm range of the multimeter to measure the resistance value of the coil (pins 1 and 2). Under normal circumstances, it is 150 to 180 ohms. If the resistance value is infinite, it indicates that the relay coil is open-circuited and should be replaced.
(2) Under normal circumstances, the two contacts on the surface of the relay are not conductive. Use the ohm range of the multimeter to measure their resistance values. If the two contacts are conductive when not powered on, it indicates that the two contacts are stuck and should be replaced.
(3) Power on to make the relay in the closed state, and its contacts should be in the same potential state, that is, in good contact.

AC Contactor

The AC contactor is an automatic controller that uses electromagnetic attraction to connect and disconnect circuits. It is mainly composed of an iron core, a coil, and contacts. The AC contactor controls the start and stop of the compressor.
Fault Phenomenon: The compressor doesn't start and doesn't work.
Detection Method:
(1) Detect the resistance value of the coil winding to see if it is open or short-circuited.
(2) Use the ohm range of the multimeter to detect the on-off condition of the upper and lower contacts of the AC contactor. Under the condition of not being powered on, the resistance value of the upper and lower contacts should be infinite. If there is a resistance value, it indicates that the internal contacts are stuck.
(3) Press the forced button on the surface of the AC contactor and use the multimeter to measure the resistance value of the upper and lower contacts. Under normal circumstances, the resistance value of each group should be zero. If it is infinite or the resistance value increases, it indicates that there may be an arc phenomenon on the surface of the internal contacts. If any of the above three phenomena occur, the AC contactor should be replaced.
Precautions:
For single-phase 3-horsepower air conditioners, when the voltage is unstable or the voltage drop is large during startup, the AC contactor is easily damaged. If there is such a phenomenon, when repairing, be sure to eliminate the power supply fault first before replacing the contactor. Otherwise, the above faults will still occur.

Receiver

The receiver in the air conditioner is mainly used to receive various operation instructions sent by the remote control and then transmit them to the main chip of the computer board to control the operation state of the whole machine.
Fault Phenomenon: The remote control has no response.
Detection Method:
Use a multimeter to measure its pins 2 and 3. When the receiving head receives a signal, the voltage between the two pins should be lower than 5V. When there is no signal input, the voltage between the two pins should be 5V. Otherwise, the component should be replaced.

Negative Ion Generator

The negative ion generator mainly emits negative ions and combines them with bacteria, particles, and smoke and dust in the air to achieve the effects of sterilization and air purification.
Fault Phenomenon: The negative ion generator doesn't work.
Detection Method:
(1) Place the negative ion detection board at the front end of the generator. When the negative ion generator is working, the light on the detection board will flash, proving that the negative ion generator is normal.
(2) Use a special electroscope. When the negative ion generator is working, the neon tube in the electroscope will flash, indicating that the negative ion is working normally.
(a) The working voltage of the negative ion generator is 12V DC or 220V AC supplied by the computer board. After being boosted by the boost transformer, it generates about 3500V DC, but its current value is very small, only a few microamps.
(b) Turn on the negative ion function and measure that there is a 12V voltage output at the plug-in position of the negative ion generator on the computer board. However, if the negative ion generator doesn't work, it indicates that the negative ion generator is faulty and needs to be replaced. In addition, if there is no 12V output to the negative ion generator on the computer board, it indicates that the computer board is faulty and needs to be replaced.

Two-way Valve

The two-way stop valve is installed on the liquid pipe side of the piping of the outdoor unit and consists of a positioning adjustment port and two mutually perpendicular pipelines. One pipeline is connected to the liquid pipe side of the outdoor unit, and the other pipeline is connected to the piping of the indoor unit through a flared nut.
Fault Phenomenon: Poor cooling and heating effects; no cooling or heating.
Common Faults and Detection Methods:
Most of the two-way valves are damaged due to improper force during installation, resulting in damage to the valve core and valve thread and causing refrigerant leakage. Use soapy water to check for leaks at the process port, valve core, and piping interface. If there is a leak point, it should be replaced.

Drier Filter

The drier filter is used to absorb moisture in the system, block impurities in the system from passing through, and prevent ice blockage and dirty blockage in the pipelines of the refrigeration system. Since the capillary tube is the part that is most likely to be blocked in the system, the drier filter is usually installed between the condenser and the capillary tube. The shell of the drier filter is formed by shrinking the red copper pipe, and metal filaments or porous metal plates are installed inside, which can effectively filter impurities.
Fault Phenomenon: Poor cooling and heating effects.
Common Faults and Detection Methods:
It is mainly caused by the metal powder generated by the mechanical wear of the compressor in the refrigeration system, some welding slag in the pipeline, and dirt in the refrigeration oil, which block the filter and hinder the circulation of the refrigerant. The main phenomenon is frosting on the surface. At this time, it should be cleaned or replaced.

One-way Valve

The one-way valve, also known as the check valve, is a valve that prevents the reverse flow of refrigerant and is composed of a nylon valve needle, a valve seat, a limit ring, and a shell. The one-way valve is mainly used in heat pump air conditioners and is connected in parallel with a section of capillary tube in the system.
Fault Phenomenon: Poor cooling and heating effects.
Common Faults and Detection Methods:
(1) Poor closing: During heating, the refrigerant passes through the one-way valve that is not tightly closed, causing the high-pressure pressure in the system to drop and resulting in poor heating effect.

(2) Blockage: When the one-way valve core is blocked, frosting will occur, resulting in poor cooling effect. In addition, when replacing the one-way valve, attention should be paid to cooling the valve body to prevent the deformation of the inner nylon valve core of the valve body and resulting in poor heating effect.
Use a pressure gauge to detect the high-pressure pressure of the system and compare it with the normal value and simultaneously observe whether the surface of the one-way valve is frosted.

Electromagnetic Reversing Valve

The electromagnetic reversing valve, also known as the four-way valve, is a control and switching valve for the conversion of the cooling and heating working states of the heat pump air conditioner.
Fault Phenomenon: When turning on the heating function, there are poor cooling and heating effects, no cooling or heating.
Common Faults and Detection Methods:
(1) Coil open circuit: After the coil is open-circuited, it cannot generate an adsorption effect on the valve core, resulting in the inability of the four-way valve to reverse and perform heating.
(2) Short circuit: When the coil of the four-way valve is seriously short-circuited, when turning on the machine for heating, a large short-circuit current will occur, burning out the fuse tube and making the whole machine unable to work.
Use the R×1K ohm range of the multimeter to measure the resistance value of the two plugs of the coil. Under normal circumstances, the resistance value ranges from 1300 to 2000 ohms according to the size of the model.

Electric Heater

In heat pump air conditioners, there are two types of heating elements, PTC type and electric heating tube type. Small air conditioners commonly use PTC type, while large and medium-sized air conditioners use electric heating tube type heaters.
Fault Phenomenon: The electric heater doesn't work.
Common Faults and Detection Methods:
The heating wire is broken, there is a short circuit between the wires, or the insulation is damaged.
(1) During maintenance, a multimeter can be used to test its resistance value. If it is infinite, it is an open circuit. If it is very small, it is a short circuit. The operation of the electric heater is generally controlled by the chip, which sends out heating instructions. When the temperature sensing bag senses that the ambient temperature is low, it starts to work. If the heater works after receiving the instruction but there is no hot air blowing out, it may be a heating wire fault or a circuit board fault. Use a multimeter to check the circuit board to see if the relay has power output.
(2) Insulation inspection method: Use a multimeter to detect the insulation resistance between the connection terminal of the electric heater and its metal shell. The value should be greater than 30 megohms.

Capacitor

The representative symbol is C. Its main functions are to store charge, filter, and shift phase. There are mainly compressor capacitors, fan capacitors, and electrolytic capacitors.
Fault Phenomenon: The compressor doesn't start, the fan doesn't work or rotates slowly.
Detection Method:
Cut off the power supply, remove the wires connected to both ends of the capacitor, and use a conductor to connect the two connection terminals of the capacitor to discharge (especially for filter capacitors. If the capacitor is not discharged and measured with electricity, it will damage the instrument). For fan capacitors and compressor capacitors, after discharging, use the R1K ohm range of the multimeter to measure. When the test leads are just connected to the two connection terminals of the capacitor, the pointer of the meter should have a large swing and then slowly return to a position close to infinite. If the pointer swing is not large, it indicates that the capacitance is small. If the pointer cannot return to a position close to infinite, it indicates that the capacitor leaks seriously and should be replaced. For electrolytic capacitors (mainly used as filter capacitors for inverter and fixed-frequency machines), the R1K ohm range of the multimeter should be used for measurement. The specific judgment method is the same as above.
Precautions:
For filter capacitors, if the capacitor is not discharged before measurement and measured with electricity, it will damage the instrument. And filter capacitors have positive and negative poles. When maintenance personnel replace the capacitor, do not reverse the positive and negative poles. Otherwise, it will cause the capacitor to break down and cause an accident.

Reactor

The representative symbol is L. It is mainly used in the DC power circuit of inverter air conditioners. Its structure is similar to that of a transformer and is composed of an iron core and insulated enameled wire. This component is fixed on the chassis of the outdoor unit. When the AC power of 220V passes through the transformer, rectifier bridge, and filter, when the current with AC components passes through the circuit with inductance, the inductance has the effect of hindering the flow of AC current and stores the excess energy in the inductance, which can improve the power factor of the power supply.
Fault Phenomenon: The outdoor unit has loud noise, doesn't start, or trips when