GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2002 🢒 Isuzu T-Series (Truck Line C) 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Leak Testing

Refrigerant Leak Testing

Tools Required

    • J 39400-A Electronic Halogen Leak Detector
    • J 41447 R-134a A/C Tracer Dye Box of 24
    •  J 41459 R-134a A/C Tracer Dye Injector
    • J 42220 Universal 12V Leak Detection Lamp
    • J 43872 Fluorescent Dye Cleaner

Important: General Motors passenger cars are now manufactured with fluorescent dye installed in the A/C system.

The preferred method of leak testing is the use of fluorescent dye. J 41447 is the only dye approved by General Motors. Follow the Fluorescent Dye Injection procedure for vehicles that do not already contain the fluorescent dye.

Fluorescent Leak Detector
    • Fluorescent dye will assist in locating any leaks in the A/C system.
    • The J 41447 dye mixes and flows with the PAG oil throughout the refrigerant system.

       Important: PAG oil is water soluble.

    • Condensation on the evaporator core or the refrigerant lines may wash the PAG oil and fluorescent dye away from the actual leak. Condensation may also carry dye through the HVAC module drain.
    • To prevent false diagnosis in the future, thoroughly clean the residual dye from any area where leaks were found. Use a rag and the approved fluorescent dye cleaner J 43872 .

Fluorescent Dye Injection

       Important: J 41447 is the only A/C leak detection dye approved by General Motors.

    • Not all of the R-134a dyes are compatible with PAG oil. Some dyes decrease the oil viscosity or may chemically react with the oil.
    • R-134a leak detection dye requires time to work. Depending upon the leak rate, a leak may not become visible for between 15 minutes and 7 days.

       Important: Do NOT overcharge the A/C system with dye. This may cause reliability problems. Use only one 0.25-ounce charge bottle of J 41447 .

    • With the A/C system charged, add J 41447 to the A/C system using J 41459 . Follow the instructions provided with J 41459 .
    • To prevent any false diagnosis, thoroughly clean any residual dye from the service port with a rag and the approved fluorescent dye cleaner J 43872 .
    • The dye injection package contains a notice sticker. Complete the leak detection information and place the sticker near the charge label.

A/C Compressor Shaft Seal Leak Detection with Dye

Use J 43872 to clean all traces of fluorescent dye from the A/C compressor shaft seal and reinspect the compressor.

  1. Run the A/C system 15-30 minutes depending on the type of leak in order to circulate the dye.
  2. Use J 42220 to inspect the A/C compressor shaft seal.
  3. To prevent a future false diagnosis, thoroughly clean any residual dye from the area of the leak with a rag and the approved fluorescent dye cleaner J 43872 .

Service Ports

The sealing cap is the primary seal for the service ports. The cap contains an O-ring gasket that provides a leak-free seal. Install the cap tightly for leak-free sealing. The following conditions will cause a refrigerant loss:

    • A loose cap
    • A missing cap
    • An incorrect cap

Use J 42220 , or J 39400-A in order to test the service ports and sealing caps for leaks.

To prevent a false diagnosis, thoroughly clean any residual dye from the service port or sealing cap with a rag and the approved fluorescent dye cleaner J 43872 .

Evaporator Core

Use J 42220 in order to inspect the HVAC drain port. Follow the Fluorescent Dye Injection procedure if the A/C system does not contain fluorescent dye.

If only J 39400-A is available complete the following steps:

  1. With the engine running, turn the A/C ON.
  2. Select the maximum blower motor speed for at least 15 seconds.
  3. Turn OFF the engine.
  4. Turn OFF the blower motor.
  5. Wait 10 minutes.
  6. Turn ON the blower motor and select the lowest speed.
  7. Insert the leak detector probe into one of the center instrument panel outlets. Try to get as close to the evaporator as possible.
  8. A solid alarm on the detector indicates a leak.

Halogen Leak Detector

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 12 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:

  1. Completely and slowly circle each joint with the probe.
  2. Place the tip of the probe as close as possible to the surface, and less than 6 mm (0.25 in) away. Do not block the probe tip air intake.
  3. A leak exists when the audible tone goes from a steady 1-2 clicks per second to a continuous alarm.
  4. Frequently adjust the balance knob in order to maintain the rate of 1-2 clicks per second.

Object Number: 82106 Size: SH

Use J 39400-A to inspect each hose connection.


Object Number: 82107 Size: SH

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


Object Number: 82101 Size: SH

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 usingJ 39400-A , follow the Fluorescent Dye Injection procedure usingJ 42220 .

A/C Compressor Shaft Seal Leak Detection with J-39400-A
  1. Blow compressed air into the following locations for at least 15 seconds:
    2. • Behind the A/C compressor clutch/pulley
    • In front of the A/C compressor clutch/pulley
  2. Wait 1-2 minutes.
  3. Probe the area in front of the pulley.
  4. Probe the area behind the pulley.
  5. A solid alarm from the detector indicates a leak.