Leak Testing - Refrigerant System
Electronic Leak Detector:
A/C Leak Scan Method:
LEAK TESTING
CAUTION: Avoid breathing A/C Refrigerant-134a and lubricant vapor or mist. Exposure may irritate eyes, nose, and throat. To remove R-134a from the A/C system, use service equipment certified to meet the requirements of SAE J221O (R-134a recycling equipment). If accidental discharge occurs, ventilate work area before resuming service. Additional health and safety information may be obtained from refrigerant and lubricant manufacturers.
A refrigerant leak test should be performed on the system whenever a leak is suspected and after performing a service operation which disturbs the components, lines, or connections. Many methods and special tools are available for this purpose; however, no matter which tool is used, care and diligence are the biggest keys to success.
ELECTRONIC LEAK DETECTOR
Tool Required:
- J 39400 Electronic Leak Detector
This type of electronic leak detector has been found to be the most useful tool in locating refrigerant leaks. The J 39400 is a small unit which operates on 12V DC and provides an audible signal which increases in frequency as R-12 or R-134a is detected. Make sure the instrument is properly calibrated, per the included instructions, and that the detector is used in the proper setting for the type of refrigerant being tested. The detector "GAS" switch should be placed in the "R-12" or "R-1 34a" setting prior to use (see accompanying figures).
The most common leaks are found at the refrigerant fittings or connections. This may be caused by improper torque, damaged O-ring seals, lack of lubricant on O-ring seals, or dirt/debris across the O-ring seals. Even the smallest piece of lint from cotton gloves or shop cloths can create a leak path across an O-ring seal.
The successful use of this and any other electronic leak detector depends greatly upon the scan rate and upon carefully following the manufacturer's instructions regarding calibration, operation, and maintenance. Each joint must be completely circled moving at 25-51 mm (1-2 inches) per second with the tip of the probe as close to the surface as possible but no more than 6 mm (0.25 inches) away and without blocking the air intake. A leak is indicated when the audible tone goes from a steady 1-2 clicks per second to a solid alarm. The balance knob should be adjusted frequently to maintain the 1-2 clicks per second rate.
IMPORTANT:
- Electronic leak detectors are sensitive to windshield washing solutions, many solvents and cleaners, and some adhesives used in the vehicle. Prevent a false warning by making sure surfaces are clean. Also, surfaces should be dry since ingestion of liquids will damage the detector.
- The evaporator inlet and outlet, accumulator inlet and outlet, condenser inlet and outlet, all brazed and welded areas, areas showing signs of damage, hose couplings, compressor rear head, and housing joints may be tested using this procedure.
- Always follow the refrigerant system around in a continuous path so that no areas of potential leaks are missed. Always test all the above areas to make sure the entire system is leak free, even when one leak is already found.
CAUTION: Take care to prevent personal injury which could occur due to touching a hot engine when testing. Tests should be done with the engine "Off" and as cool as possible. Do not operate the detector in a combustible atmosphere since its sensor operates at high temperature.
Service Portal Access Valves
The primary seal for the service ports is the sealing cap. This cap contains a specially designed O-ring seal or gasket which provides a leak-free seal. Should the cap be loose, missing, or the wrong cap used, it will result in the loss of refrigerant charge.
Evaporator Core
One of the most difficult leaks to find is in the evaporator core. To leak test the core:
1. Turn the blower fan on 'HI" for 15 or more seconds then turn it off.
2. Wait 10 minutes.
3. Remove the blower motor resistor.
4. Insert the leak detector probe as close to the evaporator as possible. If the detector goes to a sold alarm, a leak has been found.
5. If possible, visually inspect the core face with a flashlight for evidence of refrigerant oil.
Compressor Block Fitting and Shaft Seal
1. Blow shop air behind and in front of the compressor clutch/pulley for at least 15 seconds.
2. Wait 1-2 minutes.
3. Probe the area in front if the pulley. It the detector goes to a solid alarm, a leak has been found.