Note. Every time the system is opened, a vacuum must be created to protect against air and moisture ingress. After installing any element, vacuum should be maintained in the system for approximately 15 minutes. The elements of the system opened for repair must be under vacuum for 30 minutes.
If the engine does not run, perform the following procedures.
Pic. 8.60. Position «closed»
Attach a set of test gauges to the compressor fittings. Close the high and low pressure valves (pic. 8.60).
Make sure the system has been drained of refrigerant.
Attach the center hose of the gauge set to the vacuum pump inlet.
Turn on the vacuum pump and open the high and low pressure valves.
After about 10 minutes, check that the low pressure gauge shows a vacuum below 94.39 kPa (0.96 kgf/cm2). If vacuum cannot be obtained, this indicates a leak in the system. In this case, repair the leak as follows.
1. Close both valves on the pressure gauge set and turn off the vacuum pump.
2. Charge the system with refrigerant from a container (approx. 0.4 kg).
3. Locate the leak with a leak detector.
4. Drain the refrigerant again and create a vacuum in the system. If no leaks are found, continue to create a vacuum in the system.
Turn on the vacuum pump.
Open both valves of the gauge set until a vacuum of 94.39 kPa is created (0.96 kgf/cm2) (pic. 8.61).
Pic. 8.61. Position «open»
After the low pressure gauge shows a vacuum of about 94.39 kPa (0.96 kgf/cm2), continue to create a vacuum for 15 minutes.
After 15 minutes of the system being under vacuum, close both valves of the pressure gauge set and turn off the vacuum pump. Disconnect the hose from the vacuum pump. The system is ready to be charged with refrigerant.
Actions with the system charging valve
Pic. 8.62. Diagram of installation in operation with system charging valve
Before connecting the valve to the refrigerant tank, turn its handle completely counterclockwise.
Set the disc to its highest position by turning it counterclockwise.
Attach the central hose to the valve fitting.
Turn the valve handle clockwise to punch a hole in the sealed top.
Loosen the nut securing the central hose to the central fitting of the control pressure gauges.
Let the air out for a few seconds, then tighten the nut.
Charging the system with vapor refrigerant
Set the valve of the refrigerant tank to the position indicated in the section above «Actions with the system charging valve».
Note. This operation is performed to charge the system with vaporized refrigerant through the low pressure circuit. When the refrigerant tank is in a vertical position, the latter is supplied to the system in the form of steam.
Open the low pressure circuit valve and adjust its position so that the pressure on the low pressure gauge does not exceed 412 kPa (4.2 kgf/cm2).
To keep the vapor pressure of the refrigerant container slightly higher than the system pressure, place the container in a container of warm water (temperature around 40°C).
Start the engine at fast idle and turn on the air conditioner.
Note. Keep the refrigerant container upright to prevent liquefied refrigerant from entering the system through the suction line, which could damage the compressor.
Pic. 8.63. Position «closed» low pressure circuit
Charge the system with the required amount of refrigerant, then close the low pressure valve (pic. 8.63).
Amount of refrigerant to be charged: 500±25 g.
At a reduced refrigerant charge rate, immerse the refrigerant container in warm water (temperature around 40°C).
Attention! Never immerse the refrigerant container in heated water above 52°C.
Attention! It is forbidden to heat the container with a blowtorch or in a drying chamber.
Charging the system with liquid refrigerant
After vacuuming the system, fully close the high and low pressure valves.
Note. This operation is performed to charge the discharged system with liquid refrigerant through the high pressure circuit. When the container is upside down, the refrigerant is supplied to the system in the form of a liquid.
Attention! Do not charge the system through the high pressure circuit while the engine is running. When charging with liquid refrigerant, do not open the low pressure valve.
Set the valve of the refrigerant tank to the position indicated in the section above «Actions with the system charging valve».
Fully open the high pressure valve by placing the refrigerant container upside down.
Charge the system with the required amount of refrigerant by weighing it using a balance. Overcharging will result in excessive discharge pressure (in the high pressure circuit). Close the high pressure valve when charging is complete.
Amount of refrigerant to be charged: 500±25 g.
After charging the system with the required amount of refrigerant, close the control pressure gauge valve.
Use a leak detector to check that there are no leaks from the system.
Note. Before removing the control pressure gauges, it is recommended to check the operation of the system.
System leak test
Whenever a refrigerant leak is suspected or work is being done to disconnect components or loosen connections, perform a system leak test using an electronic leak detector.
Check the tightening torque of the pipeline connections. When loosening, tighten the connections to the specified torque. Use a leak detector to check for gas leaks.
If the leak persists after tightening the connection, discharge the system, disconnect the connection and check the sealing surfaces for damage. Even slightly damaged connection parts must be replaced.
Check the amount of compressor oil and top up if necessary.
Charge the system and check its tightness. If no leaks are found, vacuum purge and charge the system.
Checking the cooling capacity of the system
Install test gauges.
Start the engine and run it at 2000 rpm-1, set the temperature switch to the maximum cooled air position and the fan switch to the maximum speed.
Open all windows and doors.
Pic. 8.64. Installing a Dry Bulb Sensor in the Cooled Air Nozzle
Place the dry bulb probe into the cool air supply nozzle (pic. 8.64).
Place the psychrometer at the point where air is taken into the refrigeration circuit of the air conditioner.
Check the high pressure gauge reading, which should be between 1.373-1.575 kPa (14–16 kgf/cm2). If the reading exceeds the upper limit indicated, pour water over the condenser. If the reading is below the lower limit, cover the front of the condenser.
Check the dry bulb reading, which should be between 25-35°C.
Pic. 8.65. Psychrometric Graph
Determine the relative humidity of the air from the psychrometric graph by comparing the wet-bulb and dry-bulb temperatures of the psychrometer placed at the point where the air is taken into the air conditioner (pic. 8.65).
Note. By determining the wet-bulb and dry-bulb temperatures at the inlet of the evaporator, the relative humidity of the air can be determined. Example: The dry bulb and wet bulb temperatures at the evaporator inlet are 25°C and 19.5°C, respectively. The intersection point of the corresponding dotted lines on the graph gives the relative humidity value (60%).
Determine the temperature using the dry bulb temperature located in the cooled air supply nozzle to the passenger compartment and calculate the difference between the dry bulb temperature at the air intake and the dry bulb temperature at the air outlet to the passenger compartment.
Pic. 8.66. Relative Humidity Graph
Verify that the intersection point of the relative humidity and temperature difference lines is within the black shaded area, indicating that the cooling capacity performance is within specification (pic. 8.66).