Air conditioning common fault repair book

Section I. Air Conditioning Common Repair Tools and Usage

1. Pressure Gauge

Refrigerant leakage is a common problem with air conditioners. In order to test whether the amount of refrigerant in the system is sufficient, a pressure gauge is usually used. Pressure gauge is a common test tool in Freon refrigeration system. Its shell diameter from 60mm ~ 250mm, a variety of specifications. The vacuum pressure gauge suitable for air-conditioning refrigeration systems has a range of -0.1MPa~2.5MPa, as shown in Figure 2-33.

The pressure gauge is usually used together with a three-way repair valve. The valve hole can be narrowed by turning the three-way repair valve knob clockwise. When the knob is turned fully clockwise, the corresponding pipe will be cut off from the outdoor unit. Turning the knob counterclockwise enlarges the valve hole and the corresponding pipe is connected to the outdoor unit. Regardless of the position of the knob, the pressure gauge on the 3-way repair valve is always connected to the refrigeration system. By matching the switch of the three-way repair valve, the refrigeration system can be evacuated, charged with refrigerant and pressure tested.

2. Tube expander

When two copper tubes are butted together, it is necessary to insert one into the other. In this case, it is usually necessary to expand the inner diameter of the end of the inserted copper tube so that it can be inserted into the other copper tube in a consistent manner. Only then can the two copper pipes be soldered securely and not be prone to leakage. The purpose of the flapper is to flare copper tubes of different sizes as needed. When flaring, the annealed copper tube is first put into the corresponding aperture of the tube clamp, and the length of the copper tube extending out of the clamp varies with the diameter of the tube. For large diameter copper tube, the flaring length should be larger, while for small diameter copper tube, the flaring length should be smaller. For ф8 copper pipe, the expansion length is generally about 10mm. Tighten the nuts at both ends of the clamp, firmly clamp the copper pipe, insert the required diameter of the expansion head, slowly rotate clockwise.

3. Flashing device

Flaring is used to flare the copper pipe to connect the indoor unit and outdoor unit of the split air conditioner through the pipe. Flaring, the annealed copper pipe set of connecting nuts, and then put the copper pipe into the corresponding hole of the pipe clamp, the height of the copper pipe exposed to the pipe clamp is one-fifth of the diameter of the copper pipe. Tighten the nuts at both ends of the clamp, the tapered head of the flare presser on the mouth, slowly clockwise rotation of the screw, the mouth will be squeezed into the flare, as shown in Figure 2-35:

4. Pipe cutter

Maintenance and installation of air-conditioning, often need to use the pipe cutter to cut the different lengths and diameters of the copper pipe. The pipe cutter has different specifications, and its structure is shown in Figure 2-36:

When cutting the copper pipe, put the copper pipe between the two rollers of the pipe cutter, rotate the feed button clockwise to clamp the copper pipe between the pipe cutter and the rollers, and then rotate the feed button while rotating the pipe cutter around the copper pipe. When rotating the feed button, the force must be even and gentle, otherwise the copper pipe may be squeezed and deformed. After the copper tube is cut, use a reamer to remove the burrs on the edge of the tube opening to prevent copper chips from entering the refrigeration system.

5. Bender

The bender is used to change the shape of the copper pipe, processed into the desired shape of the tool. Benders are available in a variety of sizes and are suitable for bending radius less than 20 millimeters of copper pipe. Bending, the annealed copper pipe into the groove of the bender wheel, lock the pipe hook, slowly turn the handle to the desired angle, as shown in Figure 2-37:

6. Gas welding equipment

Most of the air-conditioning refrigeration system uses copper tubes, the maintenance of which requires gas welding. Traditional gas welding equipment uses oxygen mixed with acetylene gas, ignited to produce a high-temperature flame. Now the use of liquefied petroleum gas is more, the use of oxygen-assisted liquefied petroleum gas welder welding refrigeration system piping. Gas welding equipment mainly consists of gas cylinders, connecting hoses and welding guns.

7. Clamp watch

Clamp watch is a widely used measuring instrument, is the most commonly used tool in the electrical troubleshooting of refrigeration equipment. It can measure AC or DC voltage, AC current, resistance and so on. The object is shown in Figure 2-38:

①Measurement of AC and DC voltage.

First, switch the changeover switch to AC voltage (ACV) or DC voltage (DCV) and select a range greater than the measured voltage. Then insert the red and black probes into the jacks of the measured power outlet, and the number displayed on the panel is the measured voltage value. AC voltage has no fixed polarity, so the probe of the clamp meter can be used regardless of the positive and negative poles. When measuring DC voltage, you should turn the changeover switch to DC voltage level (DCV) and note that the range should be larger than the measured voltage. At the same time, you should determine the polarity of the measured voltage. When measuring, the red probe is connected to the positive voltage and the black probe is connected to the negative voltage. If the probe polarity is wrong, the clamp meter may be damaged.

②Measure the AC current.

Turn the changeover switch to the appropriate range of alternating current (ACA), and when measuring, just clamp the measured wire in its clamp port, and using the principle of electromagnetic induction, the display will indicate the current strength in the wire.

③Measurement of resistance.

Turn the changeover switch to the appropriate range. Before measurement, connect the two probes directly (short circuit). At this time, the display should show 0ω and sound. If the number displayed is not 0ω, the clamp is damaged or underpowered. When measuring, connect the probes to the two ends of the measured resistance, and the number shown on the screen is the measured resistance value.

Maintenance of common air-conditioning failures

Section 2, electrical control system maintenance cases

Case, bad SCR, indoor noise

Fault phenomenon:Slow rotation of the indoor fan after shutdown, and a harsh noise after startup.

Cause analysis:According to the user feedback and phenomenon analysis, the preliminary judgment of indoor motor power supply failure. Check the power supply voltage of the indoor fan. When the motor is off, there is 100 volts on the motor. After the motor is turned off, the indoor motor still runs slowly and continuously. The heat from the indoor motor caused the plastic motor frame to deform from heat and the plastic motor to shift in position. This caused the crossflow fan blades to collide with the chassis, emitting an unpleasant noise and burning odor. It was therefore determined that the fan control thyristor was damaged.

Solution:Replace the main control board.

Experience:The speed of the indoor fan of the split-hanging machine is controlled by the thyristor. When the power supply voltage is low or fluctuates greatly, it will cause single-phase breakdown of the SCR. When the indoor fan is turned off, the motor will still rotate slowly. Since the SCR is single-phase breakdown, the motor power supply is not sinusoidal, so the motor does not run smoothly and is noisy.

II. Indoor fan continues to run without starting after being turned off.

Fault phenomenon:The indoor fan will not stop after shutdown, but the fan will run without starting.

Cause analysis:According to the fault phenomenon reflected by the user, it was found that the indoor fan was running when the power was on, and it was still running when the remote control was turned off. Preliminary judgment of indoor motor power supply failure. Check the power supply voltage of the indoor fan, there is a 158V voltage output on the motor when it is energized or powered off. So the indoor motor is running after powering on, and it is judged that the fan control SCR is damaged.

Solution:After replacing the same type of controller, the debugging is normal.

Experience: the indoor fan speed is controlled by the SCR. When the power supply voltage is low or fluctuates greatly, it will cause single-phase breakdown of the SCR. When the machine is stopped or turned off, the indoor fan still has voltage, so the indoor fan cannot be turned off.

Third, the remote control receiver is broken.

Fault phenomenon:The remote control does not start.

Analysis:Check the remote control, the remote control to the ordinary radio, press any key on the remote control. The radio will respond, indicating that the remote control is normal, the fault is in the indoor machine main control board or remote control receiver. Open the cover of the indoor unit, check whether the 220v input power and 12v, 5v voltage is normal. Manually start the air conditioner, the air conditioner can start and run normally, indicating that the main control board is not a problem, the fault is in the components of the remote control receiver. Upon inspection, it was found that the ceramic capacitor (103Z/50v) on the controller receiver circuit has a small insulation resistance of only a few kω, and the high-quality ceramic capacitor should be more than 10,000mω, generating leakage current.

Solution:Cut off the 103 capacitor directly or replace the display panel, the air conditioner has been running normally.

Summary:There are many reasons for not receiving the remote control signal. In addition to the above capacitance leakage, all parts of the virtual welding will also cause not to receive. In addition, the use of air conditioning environment on the remote control reception is also a big impact. When the humidity is high, condensation condenses on the feet of the solder joints on the back of the remote control display panel, the circuit board becomes moldy, and the insulation decreases. There is leakage between the solder joints, resulting in the remote control not starting or remote control failure. Clean the circuit board, dry it with a hair dryer, solder a layer of glass adhesive on the back of the remote control display panel, and the AM position of the radio can be used to detect whether the remote control transmits a signal. If the air conditioner runs normally after manual start, the main control board failure can be ruled out, so it can be determined that the problem is in the receiver. When repairing, accessories should not be simply replaced, especially if the repair is repeated within a short period of time. The cause of damage to the accessory should be carefully analyzed.

Case four. Temperature sensor failure

&8226;Failure phenomenon:Air conditioning heating effect is poor, the wind speed has been very low.

&8226;Analysis:On-site inspection, the fan motor is hot, the wind speed is very low, and the air outlet is hot. When the air conditioning mode is changed, the air speed can be adjusted high and low in the cooling and air supply mode, and the high and low air speeds are obvious, proving that the fan motor is normal. It is suspected that the characteristics of the indoor tube temperature sensor have changed.

Solution:After replacing the indoor tube temperature sensor, debugging everything is normal.

General experience: air conditioning heating, because of the function of anti-cold air, indoor temperature sensor indoor heat exchanger at 25 degrees Celsius or more to work with the breeze, at 38 degrees Celsius or more to work with a set wind speed. First observe that the wind speed is low and the air temperature is high, check whether the fan is normal. When the wind speed is normal, analyze the temperature detected by the sensor may be incorrect, causing the indoor fan not to operate at the set wind speed, replace the sensor.

Temperature sensor failure in the air conditioning failure accounts for a large proportion. To accurately determine, first of all, to understand its function. Air conditioning control components in three temperature sensors:

1. Room temperature sensor: the main detection of indoor temperature. When the indoor temperature reaches the set requirements, it controls the operation of the internal and external units. When cooling, the external unit stops while the internal unit continues to run. When heating, the internal unit stops after blowing residual heat.

2. Indoor Tube Temperature Sensor: It mainly detects the indoor evaporator coil temperature, and plays a role in preventing cold air, overheating, and automatic temperature control during heating. If the coil temperature just started does not reach 25℃, the indoor fan will not run; when the temperature reaches 25℃ to 38℃, the indoor fan will work with the breeze; when the temperature reaches 38℃ or above, it will work at the set wind speed; when the indoor coil temperature reaches 57℃ for 10S, the outdoor fan will stop running, and the compressor will stop running when the temperature is over 62℃ for 10S. . Only when the temperature drops to 52℃, the outdoor unit will be put into operation. Therefore, when the coil resistance is greater than normal, the indoor unit may not start or keep running at low air speed. When the coil resistance is low, the outdoor unit will frequently stop the indoor unit to blow cold air. Provides freeze protection when cooling. The outdoor unit stops when the indoor coil temperature falls below -2 degrees Celsius for 2 minutes. When the indoor coil temperature rises to 7 degrees Celsius or the compressor stops working for more than 6 minutes, the outdoor unit continues to run. Therefore, when the coil resistance is too high, the outdoor unit may stop running and the indoor unit blows natural air, resulting in a non-cooling malfunction.

3. Outdoor defrost temperature sensor: mainly detects the temperature of the outdoor condenser coil.

When the outdoor coil temperature is lower than -6℃ for 2 consecutive minutes, the indoor unit will enter the defrost state. When the resistance of the outdoor coil sensor is too large, the indoor unit will not work properly.

5. Case:Air conditioner does not cool, communication failure.

Failure phenomenon: the indoor unit "running" light flashes (other lights off), the internal and external machine does not work.

Cause analysis:According to the user, the machine starts normally, but no user reflects. But after about 30 minutes, the inner and outer machine stopped working, the running light on the control panel flashed, and the air conditioner did not respond by pressing any key. After unplugging the power supply, the machine can work normally, but the same fault occurred after 30 minutes. Because the air conditioning and cooling were normal before the machine was turned off, the system would not have a problem. Initial judgment is an external signal problem, fault code display from the company.

Solution:Connect 103 ceramic chip capacitors in parallel between the signal lines of the computer board, or replace the anti-interference C3Y computer board produced by Fahua to eliminate the problem.

Experience:When repairing, we should be good at observing the indication status of the panel when the fault occurs, and quickly find out the cause of the fault according to the fault code provided by the company. If the outdoor pipe temperature sensor failure or inside and outside the signal connection line open circuit, no digital display function of the "timing indicator" flashes once a second; if there is a digital display function, it will display the E2 code, three-phase A series of "temperature light" flashes, all other Indicator light is off.

Sixth, the external signal interference

Fault phenomenon: irregular automatic shutdown at work, and accompanied by a buzzer abnormal continuous beeping.

Analysis:Check the remote control is normal, the emergency is normal, indicating that the power supply is normal, the motherboard is normal, the measurement of the internal unit of all sensors is normal. In accordance with the user's statement, at the same time to buy two units of the same model of air conditioning, a normal, a failure. Suspect a source of interference. The room where the faulty machine is found is equipped with electronic rectifier energy-saving lamps, and the machine is normal no matter when the lights are turned off. When the lights are on, measure the signal input of the receiver has 2V AC. When the light is off, the remote control does not work, measure the voltage is 0 V. The machine is normal.

Solution:Suggest users to replace the electronic rectifier fluorescent lamp brand, the machine is normal.

Experience:Electronic rectifier fluorescent lamps produce frequencies and waveforms superimposed on the infrared waveforms emitted by the remote control, resulting in the machine receiving abnormalities, frequency interference sources. Before repairing such faults, the user should be carefully asked about the use of the method, and observe the external environment of the machine. The signal interference source of air conditioning is divided into electromagnetic interference, frequency interference and infrared interference with poor power quality, and this fault belongs to the former. In processing, you can add a transparent dark-colored filter baffle in front of the remote control receiver head, or add a magnetic ring on the harness of the receiver board, or replace the modified controller.

Seven, the power supply phase sequence protection

Trouble phenomenon: when the power on, the "timing" light and "run" light flashes at the same time, the system stops.

Reason analysis: according to the fault code for outdoor protection, the compressor forced to run, normal operation, check the pressure switch is normal, the power supply is also normal. Preliminary judgment for the phase sequence detection protection, the phase sequence is connected to the compressor suddenly reversed, confirmed to belong to the phase sequence detection board failure.

Solution:Replace the outdoor unit test board after the air conditioning operation is normal.

Summary of experience: according to the fault code one by one elimination, maintenance personnel should have a certain circuit working principle maintenance experience. In the detection of faults, should follow the interval and complexity, so as to avoid detours (according to the above, after adjusting the phase sequence, reverse turn on the compressor, at this time, only need to adjust the compressor wiring to solve the problem).A series of three-phase power supply, the installation of the installer will sometimes be the phase line and the zero line together, but also lead to the compressor can not be started. During maintenance, it is necessary to

Eight, FS, DS control panel button failure

Failure:Control panel button malfunction, the remote control can be operated.

Analysis:Because you can receive the remote control operation, it can be ruled out is the problem of the computer motherboard. After investigation, Changzhou Hongdu production of the display board for key scanning D1 ~ D12 diodes used in low-frequency diodes IN4007, while the main program in the key processing is high-frequency; individual control panel and its own motherboard is incompatible with the main program can not correctly respond to the key operation of the key issued by the signal, resulting in the failure of the key operation. Control panel and motherboard failures are mainly caused by products manufactured before February 2004 by Changzhou Hongdu Electronics Co.

Solution: When such failures are found, you can replace the control panel produced by Changzhou Hongdu Electronics Co., Ltd. after February 2004 or other companies with our matching control panel, or the control panel on the D1 ~ D12 diode replacement for IN4148 high-frequency tube.

Summary: In addition to the DS key failure, FS (Y) temperature adjustment button may also fail. Display panel design takes into account the key touch leaves a small gap, plastic factory plastic panel deformation, and the middle panel gap is too small, resulting in operational failure. If this failure occurs, simply replace the control panel of the same model.

Nine, the compressor can not start at low pressure

Fault phenomenon: the compressor outside the machine does not start when starting.

Reason analysis: the indoor machine works normally, the controller outside the compressor voltage output is normal, measured compressor capacitance is normal. So is the compressor problem. Compressor resistance value of each winding is normal. Measuring the user voltage, found that the voltage is only 198V, but within the range of standard design criteria, so the compressor (48D129) start performance is poor.

Solution:Replace a 35UF special capacitor for the compressor, and connect an auxiliary starter in parallel with the compressor capacitor. The air conditioner turns on normally without replacing the compressor.

X. Compressor capacitor and fan capacitor

Failure phenomenon:During refrigeration, when the compressor starts, the air switch trips.

Reason analysis: the air conditioner is turned on cooling operation, the compressor started on the trip, a separate test of the indoor unit is running normally, to determine the fault in the outdoor unit. Open the outdoor unit shell, check the resistance of the power line L and N at both ends is ∞, to ensure that there is no short circuit between the two lines or a short circuit to ground, and then check the outdoor equipment one by one. When checking the compressor capacitor, the capacitor was found to be shorted.

Solution:Replace the compressor capacitor, debugging normal.

Experience:When the air conditioning compressor starts to trip, first check whether the power supply L, N line is short-circuited, and then confirm whether it is indoor or outdoor, and then continue to check whether the internal and external components are short-circuited.

Situation 11:Bad external fan capacitor.

Failure phenomenon:Frequent shutdown, poor results.

Analysis:Air conditioning installation for more than a year, used in a restaurant, power supply 220 V. Users reflect the air conditioning work for a period of time, a moment of refrigeration a moment of non-refrigeration, can not work properly. Door-to-door inspection pressure 5Kg, current 12.5A suspect that the condenser is too dirty. After cleaning the condenser, the fault is still not eliminated. Observe the outdoor unit, found that the air conditioning work outside the fan motor rotates slowly, work 30 minutes after the fan stops, the compressor current rises to stop. At this time &8226; Solution:Replace the fan and capacitor, debugging normal.

Summary:According to the test can be concluded: fan protection is due to the failure of the fan capacitor, the fan stops after the system heat dissipation is poor, resulting in the compressor due to overcurrent and stop, three minutes after the compressor and restart. This is repeated, resulting in frequent starting and stopping. It can be seen that some failures are caused by a variety of reasons, caused by the interaction between the electronic control and the system. So the maintenance should be carefully checked and observed, and less detours.

Twelve, the transformer is bad.

Failure phenomenon: start no response.

Cause analysis:According to fault analysis, first check the power supply, there is 220V input, to rule out power problems. Measure the resistance of the power plug L and N is infinite, which may cause the fuse to blow or the transformer to burn out. Open the indoor unit panel to check the main board, the fuse is good. Measuring the transformer, found that the primary open circuit.

Solution:Replace the transformer, test the machine normally and troubleshoot the problem.

Experience:If the whole machine is not responsive when repairing, start from the power supply circuit first, so that we can quickly and accurately find out the fault.

Case XIII. AC contactor

Fault:No heating.

Cause analysis:The machine starts to heat up, the outer fan rotates, the compressor does not rotate, the four-way valve is closed, measure the relay output of the four-way valve on the inner board, the AC contactor is normally energized, force the AC contactor to be pressed, the compressor starts, and then the AC contactor coil is disconnected.

Solution:Replace the AC contactor for debugging is normal.

Experience:If the internal unit power supply is normal, the external fan and 4-way valve are normal, and the compressor does not work, first check whether the contactor is closed or not, and whether the coil resistance is normal or not, and then check the compressor problem. AC contactor damage is usually caused by burnt coils, loose, dirty and burnt contacts.

Case 14:Power line problem

Fault:No cooling.

Analysis:Turn on the power, the internal machine works normally. Observe the external machine, the press start "humming" sound, can not start normally. Measured voltage from 230V to 138V, the press is protected. Determine that there is a problem with the power supply. By checking the user's power outlet, found that the renovators use the ground wire as the zero line, after processing the commissioning is normal.

Solution:Connect the ground wire to the zero wire.

Experience:When installing, you must use the N terminal to connect the zero wire, not the ground wire. Reversing the ground and zero wires may also cause the air switch to trip. It is necessary to check the power supply when this problem occurs in a new installation. Sometimes the power supply wiring is too thin and the air conditioner starts up with a high current, and a large voltage drop across the wires can also cause starting difficulties. In addition to power cord problems, the size of the air switch often causes startup trips.