Heating and Air Conditioning: Service and Repair
Operation Procedure for Charging A/C with Refrigerant
Recovery
When discharging refrigerant out of A/C system, always recover it by using refrigerant recovery and recycling equipment (1). Discharging refrigerant HFC-134a (R134a) into atmosphere would cause adverse effect to environments.
NOTE:
- After recovering refrigerant from system, the amount of removed compressor oil must be measured for replenishing. Refer to Precautions on Replenishing Compressor Oil Precautions on Replenishing Compressor Oil.
- When handling recovery and recycling equipment, be sure to follow the instruction manual for the equipment.
Evacuation
NOTE:
Attempting to evacuate the A/C system when refrigerant remains in the system will damage the vacuum pump.
Do not evacuate the A/C system before completely recovering the refrigerant from the system.
NOTE:
Once A/C system circuit is opened (exposed to atmospheric air), air conditioning system must be evacuated by using a vacuum pump. The A/C system should be attached with a manifold gauge set, and should be evacuated for approx. 20 minutes.
1) Connect high charging hose (1) and low charging hose (2) of manifold gauge set (3) respectively as follows:
High charging hose (1) -> High pressure charging valve (4) on discharge hose
Low charging hose (2) -> Low pressure charging valve (5) on suction pipe
2) Attach center charging hose (6) of manifold gauge set (3) to vacuum pump (7).
3) Operate vacuum pump (7), and then open discharge-side valve (9) (Hi) of manifold gauge set (3).
If there is no blockage in the system, there will be an indication on high pressure gauge (10).
In this case, open the other-side valve (8) (Lo) of the set and repair the system.
4) Approx. 10 minutes later, low pressure gauge (11) should show a vacuum lower than -100 kPa (-1.0 kg/cm2, -760 mmHg, -14.2 psi) providing no leakage exists.
NOTE:
- If the system does not show a vacuum below -100 kPa (-1.0 kg/cm2, -760 mmHg, -14.2 psi), close both valves, stop vacuum pump and watch movement of low pressure gauge.
- Increase in the gauge reading suggests existence of leakage. In this case, repair the system before continuing its evacuation.
- If the gauge shows a stable reading (suggesting no leakage), continue evacuation.
5) Evacuation should be carried out for a total of at least 20 minutes.
6) Continue evacuation until low pressure gauge indicates a vacuum less than -100 kPa (-1.0 kg/cm2, -760 mmHg, -14.2 psi), and then close both valves (8), (9).
7) Stop vacuum pump (7). Disconnect center charging hose (6) from pump inlet. Now, the system is ready for charging refrigerant.
Checking of A/C System for Pressure Leaks
After completing the evacuation, close manifold gauge high pressure valve (Hi) and low-pressure valve (Lo) and wait 10 minutes. Verify that low-pressure gauge reading has not changed.
NOTE:
If the gauge reading moves closer to "0", there is a leak somewhere. Inspect the tubing connections, make necessary corrections. And then evacuate system once again and make sure that there are no leaks.
Charge
WARNING:
There is a risk of personal injury or health problems if the A/C system is charged with refrigerant incorrectly or if refrigerant containers are improperly handled.
Be sure to take the following precautions to reduce the risk of injury or health problems.
- Be sure to perform the refrigerant charge operation with the engine stopped. Charge the high-pressure side first and then the low-pressure side. If you do not, the refrigerant may flow backward and cause the hose or refrigerant container to burst.
- Install the tap valve carefully following the instructions on the refrigerant container to prevent contact with the refrigerant.
- Be sure to empty the refrigerant container before discarding it to prevent possible health problems and other dangerous consequences.
- Never expose the refrigerant container to a heat higher than 40 °C (104 °F). Liquid refrigerant will turn into a toxic gas.
NOTE:
Failure to take proper precautions when charging the A/C system can result in charging the system with the incorrect amount of refrigerant and can lead to poor system operation or damage to system components.
- Since the A/C system has no sight glass, first recover refrigerant and evacuate the system, and then fill the system with the specified amount of refrigerant.
- Charge the system only when the compressor is not hot to assure that you have used the correct amount of refrigerant.
- Be sure to check the pressure gauges before and during charging to assure that there is the correct amount of refrigerant in the system.
- Do not turn the refrigerant container upside down during charging. Doing so will cause liquid refrigerant to enter the compressor and damage it.
NOTE:
The A/C system contains HFC-134a (R-134a).
Described here is a method to charge the A/C system with refrigerant from the refrigerant service container.
When charging refrigerant recovered by using the refrigerant and recycling equipment (when recycling refrigerant), follow the procedure described in the equipment manufacturer's instruction manual.
Charge system with proper amount of refrigerant accurately in accordance with the following procedure.
Specified amount of refrigerant
530 ± 30 g (18.6 ± 1.0 oz)
The initial charging of the A/C system is performed from the high-pressure side with the engine stopped.
And next, this method must be followed by charging from the low-pressure side with the engine running.
1) Check to make sure that hoses are routed properly after evacuating the system.
2) Connect low charging hose (1) and high charging hose (2) of the manifold gauge set (3) in position. Thus open refrigerant container valve (4) to purge the charging line.
3) Open the high-pressure side valve (6) and charge system with refrigerant.
4) After a while, open the low-pressure side valve (5) and close the high-pressure side valve (6).
WARNING:
If the high-pressure side valve is not closed securely, the refrigerant may flow backwards and cause the hose or refrigerant container to burst, possibly resulting in a personal injury.
Be sure to close the high-pressure side valve securely.
5) Start engine and keep engine speed at 1,500 rpm. Then, operate A/C system.
6) Charge A/C system with refrigerant in vapor state. At this time, refrigerant container should be held upright.
7) When refrigerant container (3) is emptied, use following procedure to replace it with a new refrigerant container (3).
a) Close low pressure valve.
b) Replace empty container (3) with a refrigerant container which has been charged with refrigerant. When using refrigerant container tap valve (4), use the following procedure for replacement.
i) Retract needle (1) and remove refrigerant container tap valve (4) by loosening its plate nut (2).
ii) Install previously-removed refrigerant container tap valve (4) to a new refrigerant container (3).
c) Purge any air existing in center charging hose.
When using refrigerant container tap valve, use the following procedure to purge air.
i) Once fully tighten refrigerant container tap valve and then loosen (open) plate nut slightly.
ii) Open low pressure valve of manifold gauge set a little.
iii) As soon as refrigerant comes out with a "hiss" (1) through a clearance between refrigerant container and tap valve, tighten plate nut as well as manifold gauge set low pressure valve.
iv) Turn handle of tap valve clockwise so that its needle is screwed into the new container to make a hole for refrigerant flow.
8) After the system has been charged with specified amount (530 ± 30 g) of refrigerant or when low pressure gauge and high pressure gauge have indicated the following specified value, close low pressure side valve on manifold gauge set.
Low side and high side pressure example
Removal of Manifold Gauge Set
WARNING:
If the manifold gauge set is removed carelessly, refrigerant under pressure may spray out of the high-pressure side of the A/C system. The refrigerant could contact your eyes or skin, causing injury.
Remove the manifold gauge set carefully, following the instructions provided below.
For the A/C system charged with the specified amount of refrigerant, remove manifold gauge set as follows:
1) Close low pressure side valve of manifold gauge set. (The high pressure side valve is closed continuously during the process of charging.)
2) Close refrigerant container valve.
3) Stop engine.
4) Using shop rag, remove charging hoses from service valves. This operation must be performed quickly.
5) Put caps on service valves.
Check A/C System for Refrigerant Leaks
Whenever a refrigerant leak is suspected in the system or any service operation has been performed which may result in malfunction lines and/or connections, it is advisable to check for leaks.
Common sense should be used in performing any refrigerant leak test, since the need and extent of any such test will, in general, depend upon the nature of a complaint and the type of a service performed on the system.
Liquid leak detector
WARNING:
If the refrigerant is exposed to a fire, it turns to a poisonous gas (phosgene).
Do not inhale the gas that is produced if refrigerant is exposed to a fire.
There are a number of fittings and places throughout the air conditioning system where a liquid leak detector solution may be used to pinpoint refrigerant leaks.
By merely applying the solution to the area in question with a swab, such as attached to the bubbles will form within seconds if there is a leak.
For confined areas, such as sections of the evaporator and condenser, an electronic (gas) leak detector is more practical for determining leaks.
Special Tool
(A): 09990-86012
