Electronic Leak Detection Method

Tools Required 

J 39400  Electronic Halogen Leak Detector

Use the J 39400  in order to locate refrigerant leaks. The J 39400  provides an audible signal that increases in frequency if the unit detects refrigerant.

There are 3 settings:

• The R-134a setting
• The R-12 setting
• The gross leak setting

Use the gross leak setting in order to isolate very large leaks that you found by using another setting. Correctly calibrate the instrument according to the instructions. Set the detector to the refrigerant setting that is correct for the system being tested. Place the detector GAS switch in the R-134a setting prior to use.

The successful use of an electronic leak detector depends greatly upon the following conditions:

• The scan rate
• Correct calibration, operation, and maintenance of the detector, according to the manufacturer's instructions

  Important:  Halogen leak detectors are sensitive to the following items in a vehicle:

• Windshield washing solutions
• Solvents and cleaners
• Some adhesives

Follow the refrigerant system in a continuous path in order to ensure that you do not miss any areas of potential leaks. Verify that all areas of the system are leak-free, even if you already found one leak.

1. Verify that the surfaces are clean in order to prevent a false warning.
2. Verify that the surfaces are dry, because the ingestion of liquids damages the detector.
3. Blow out the engine compartment using an air hose prior to the test. The presence of vapors may cause a false warning.
4. Move the probe of the J 39400  completely around each joint.
   Fig 1: Moving Probe Around Joint

   Courtesy of GENERAL MOTORS CORP.
5. Move the probe at a rate of 25-50 mm (1-2 in) per second.
6. Keep the tip on the probe as close to the surface as possible.

   Keep the tip closer than 6 mm (1/4 in) from the surface. Do not block the air intake of the probe.

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

   If the steady 1-2 clicks per second changes to a solid alarm, a leak is present.

Fig 2: Testing Joints And Couplings

Courtesy of GENERAL MOTORS CORP.

Test the following areas:

• The pressure sensor
• The receiver-dryer inlet
• The receiver-dryer outlet
• The evaporator inlet
• The evaporator outlet
• The condenser inlet
• The condenser outlet
• The compressor inlet
• The compressor outlet
• Other connections
• All the brazed areas
• All the welded areas
• Areas that show signs of damage
• Hose couplings
• The compressor rear head and the housing joints

Fig 3: Testing All Points For Leak

Courtesy of GENERAL MOTORS CORP.