Electronic Leak Detectors

Electronic Leak Detector:

Tool Required:
J 39400 Electronic Leak Detector

This type of leak detector has been found to be the most useful tool in locating refrigerant leaks. The J 39400 is a small unit that operates on 12V DC and provides an audible signal that increases in frequency as R-134a is detected. Make sure the instrument is properly calibrated, according to 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-134a" setting prior to use.

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. Adjust the balance knob frequently to maintain the 1-2 clicks per second rate.

Caution: Halogen 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.


Important: 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.


WARNING: Take care to prevent personal Injury that could occur when touching a hot engine while 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.