Halogen Leak Detector

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CAUTION: Do not operate the detector in a combustible atmosphere since its sensor operates at high temperatures or personal injury and/or damage to the equipment may result.

Ensure that the vehicle has at least 0.45 kg (1 lb) of refrigerant in the A/C refrigeration system in order to perform a leak test. Refer to REFRIGERANT RECOVERY AND RECHARGING for recharging the A/C system.

Important: Halogen leak detectors are sensitive to the following items:

Windshield washing solutions
Many solvents and cleaners
Some adhesives used in the vehicle

Clean and dry all surfaces in order to prevent a false warning. Liquids will damage the detector.

Important: Follow a continuous path in order to ensure that you will not miss any possible leaks. Test all areas of the system for leaks.

The J 39400-A is a small unit that operates on volts DC. The J 39400-A provides an audible signal that increases in frequency as the unit detects R-134a. Follow the instructions included with the unit in order to properly calibrate the instrument. Use the detector in the proper setting for the type of tested refrigerant.

The most common leaks occur at the refrigerant fittings or connections. The leaks may be the result of any of the following conditions:

Improper torque
Damaged O-rings or sealing washers
Lack of lubricant on O-rings
Dirt or debris across the O-ring or sealing washers

Maintain a proper scan rate in order to successfully use the J 39400-A or any other electronic leak detector. Carefully follow the manufacturer's instructions regarding the following items:

Calibration
Operation
Maintenance

In order to test for leaks, complete the following steps:

Completely and slowly circle each joint with the probe.
Place the tip of the probe as close as possible to the surface, but no more than 6 mm (0.25 in) away. Do not block the probe tip air intake.
A leak exists when the audible tone goes from a steady 1-2 clicks per second to a continuous alarm.
Frequently adjust the balance knob in order to maintain the rate of 1-2 clicks per second.

Fig 1: Inspecting Hose Connection With Leak Detector
Courtesy of GENERAL MOTORS CORP.

Use J 39400-A to inspect each hose connection.

Fig 2: Inspecting Electrical Sensors And Switches With Leak Detector
Courtesy of GENERAL MOTORS CORP.

Use J 39400-A to inspect all the electrical sensors and switches located in the A/C lines.

Fig 3: Inspecting Service Ports With Leak Detector
Courtesy of GENERAL MOTORS CORP.

Use J 39400-A to inspect the service ports.

If you know that the system has lost the refrigerant charge and you cannot find a leak using J 39400-A , follow the Fluorescent Dye Injection procedure using J 42220 .