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.

Perform a refrigerant leak test on the system whenever you suspect a leak. Also perform a refrigerant leak test after a service operation which disturbs any of the following items:

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.

Tools Required

J 39400-A Halogen Leak Detector

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

Use this procedure in order to test the following components:

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.

This type of leak detector is the most useful tool to locate refrigerant 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. Set the detector gas switch to R-134a prior to use.

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

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:

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, but no more 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.

Using the J 39400-A , check each hose connection.

Using the J 39400-A , check all the electrical sensor and switches located in the lines.

Using the J 39400-A , check the service ports.

Tools Required

Important: 

If you know that the system has lost charge and you cannot find a leak with the J 39400-A , use a leak detection dye. This dye mixes with R-134a PAG oil. When you inspect the leak locations with a J 42220 , the dye glows yellow/green.

The dye package contains a refrigerant leak detection notice sticker. Complete the sticker information and place the sticker near the charge label.

With the A/C system charged, use the instructions provided with the new R-134a leak detection dye injector tool J 41459 .

To prevent a false diagnosis after dye injection, thoroughly clean any residual dye from the access port with a rag and the approved fluorescent dye cleaner J 43872 or equivalent. After diagnosing a leak using dye, be sure to clean all residual dye from the repaired area.

The primary seal for the service ports is a sealing cap. The cap contains an O-ring or gasket that provides a leak-free seal. This cap must be installed and tight for leak-free sealing. The following conditions will cause a refrigerant loss:

One of the most difficult leaks to find is in the evaporator core. Complete the following steps in order to test the core for leaks:

1. Turn the blower on HI for 15 or more seconds. Turn the blower off.
2. Wait 10 minutes.
3. With the blower on the lowest speed insert the leak detector probe into one of the center instrument panel outlets. Try to get as close to the evaporator as possible.
4. A solid alarm on the detector indicates a leak.
5. An evaporator core leak may be detected after a dye injection by using the J 42220 to inspect the drain port area.

1. Blow compressed air into the following locations for at least 15 seconds:

•	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. A solid alarm on the detector indicates a leak.

When leak testing a A/C compressor shaft seal using the leak detection dye method, there may be some seepage of dye from the seal, for the seal is a dynamic seal.

1. Use the instructions provided with the new R-134a leak detection dye injector tool J 41459 and inject dye into the vehicle's A/C system.
2. Run the A/C system 15 to 30 minutes (depending on the type of leak) to circulate the dye.
3. Using the J 42220 check for a leaking A/C compressor shaft seal.
4. If a leak is found, verify the leak with theJ 39400-A because of the possible shaft seal seepage.
5. Make the necessary repair.
6. Clean the area of the leak after the repair so that residual dye does not indicate a false diagnosis in the future. Use a rag and the approved fluorescent dye cleaner J 43872 or equivalent to remove the excess dye.