Common methods for bus hvac system
analyzing faults are generally through four aspects: listening, seeing, touching, and measuring.
Listen: (It means to pay attention to whether there is any abnormal noise in the bus air conditioning
system. It includes listening to the bus engine, compressor, evaporating fan, condensing fan, relay, etc. When the air conditioning solutions for bus
is started and the compressor starts to work, the sound of the engine increases slightly. Big, as a normal phenomenon, as a maintenance personnel should also listen to the introduction of the bus driver.
Look: Take a close look at the following items:
✱Pressure, water temperature, oil pressure and various performance indicators on the bus dashboard;
✱Signal indicators on the control panel of the air conditioning system;
✱Check the piping system, whether there are any signs of leakage at each joint, and whether there is oil pollution on the joints;
✱ Observe the flow of refrigerant in the sight glass;
✱Observe whether there is condensation, frost, icing, etc. on the surface of the refrigeration parts of the air conditioning system;
✱Observe whether there is any burn on the electrical contacts.
Touch: touch means to feel the operation of the air conditioning system with your hands after turning on the air conditioning system for a period of time;
✱Feel the temperature and air volume of the air-conditioning outlet in the compartment with your hands;
✱Alternately touching the exhaust pipe and return pipe of the compressor with hands should have a significant temperature difference;
✱Alternately touching the drain pipe and intake pipe of the condenser with hands, the discharge temperature should be lower than the intake temperature;
✱Touch the temperature at both ends of the dryer alternately with your hands, and there should be no heat in the front and cool in the back;
✱Touch the temperature at both ends of the expansion valve alternately with your hands. It should be that the inlet is hot and the outlet is quite cold.
Note: When touching the air conditioning system with your hands, please be buseful not to let the high-speed rotating parts hurt you, and don't let the engine burn your skin!
Test: Through the process of listening, watching and touching, only the external manifestations of abnormal phenomena can be found. To make accurate conclusions, the air conditioning system should be tested with the help of pressure gauges, leak detectors, multimeters, anemometers, tachometers and other instruments , busefully analyze the test results and failure symptoms, find out the failure, and then eliminate it.
Visual inspection (visual inspection, hand feeling, hearing)
① Check the air volume of the air outlet of the air conditioner. If the air volume is insufficient, check the air intake filter and the evaporation
If there is any dirt, remove it;
②Listen to see if there is any abnormal sound near the compressor, if so, check the installation of the compressor
③Check if there is any dirt on the cooling fins of the condenser, and if so, remove the dirt;
If there is leakage, the connection should be tightened or the parts there should be replaced;
⑤Turn on the fan to low, medium and high levels, listen to whether there is any noise at the fan, check whether the fan is running
Turn to normal.
Check the amount of refrigerant
There are two ways to check the amount of refrigerant, one is to check through the sight glass installed in the system, and the other is to check by detecting the system pressure.
A.Check the amount of refrigerant through the sight glass (see above)
B. Check the amount of refrigerant by checking the pressure of the system
Connect the manifold pressure gauge: turn off all the high and low pressure switches of the manifold pressure gauge;
Connect one end of the fill hose to the manifold air gauge and the other end to the service valve on the vehicle side:
Blue hose → low pressure side red hose → high pressure side Note:
When connecting, fasten the filling hose by hand instead of any tools; if the connection seal of the filling hose is damaged, replace it;
Be buseful not to install the hose backwards when connecting the low-pressure side and the high-pressure side; do not bend the pipe when connecting to the multi-function meter.
Check the pressure of the refrigeration system: Start the engine and check the pressure displayed on the manifold gauge while the air conditioner is running.
Normal pressure reading range:
Low pressure side: 0.14～0.32MPa (1.4-3.2kgf/cm2) High pressure side: 0.8～1.7MPa (8-17kgf/cm2)
Note: The pressure value varies with the temperature inside the bus, the outside air temperature and the speed of the compressor g5k5t38m.