Caution: Do not operate the detector in a combustible atmosphere since its sensor operates at high temperature. Personal injury or damage to the equipment may result.

Perform a refrigerant leak test on the system whenever you suspect a leak due to the following conditions:

Many methods and special tools are available for this purpose.

Tools Required

J 39400

This type of leak detector is the most useful tool in locating refrigerant leaks.

There are 3 settings:

The gross leak setting is for isolating very large leaks already found in one of the other two settings. Ensure that the instrument is properly calibrated, per the included instructions. Ensure that the detector is used in the proper setting for the type of refrigerant system being tested. Place the detector GAS switch in the R-134a setting prior to use.

Prior to beginning the test, ensure that the refrigerant system is sufficiently charged for leak testing by measuring the static pressure using a gauge set. System pressures above 50 psi are acceptable to conduct a leak test.

The most common leaks are found at the refrigerant fittings or connections. Leaks may result from the following conditions:

The smallest piece of lint from the following items may create a leak path along an O-ring:

The successful use of this and any other electronic leak detector depends greatly upon the following conditions:

Completely circle each joint moving at 25 to 50 mm (1 to 2 inches) per second. Ensure that the tip on the probe is as close to the surface as possible but no more than 6 mm (1/4 inch) away and without blocking the air intake. A leak is indicated when the audible tone goes from a steady 1 to 2 clicks per second to a solid alarm. Adjust the balance knob frequently in order to maintain the 1 to 2 clicks per second rate.

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

Test the following areas using this procedure:

Important: Always follow the refrigerant system around in a continuous path in order to ensure that no areas of potential leaks are missed. Always test all of the above areas in order to ensure that the entire system is leak-free, even when one leak is already found.

The primary seal for the service port is the sealing cap. This cap contains a specially designed O-ring or gasket that provides a leak-free seal. A loss of refrigerant charge may result under the following conditions:

The high side port is identified with a red cap. The low side port is identified with a blue cap.

One of the most difficult leaks to find is in the evaporator core. The core is encapsulated into a closed module. The core is inaccessible to leak detector devices. Use the following procedure in order to test the core:

1. Turn the blower fan on HIGH for 15 seconds. Shut the fan off.
2. Wait 10 minutes.
3. Remove the blower motor or the blower resistor.
4. Insert the leak detector probe into the opening. The detector going to a solid alarm is an indication that there is a leak.
5. If possible, use a flashlight in order to visually inspect the core face for evidence of refrigerant oil.

A defective or a worn-out shaft seal often causes compressor gas leaks. A small amount of compressor oil leakage from the shaft seal is normal. Replace the compressor only when a large leak is detected. At times, an oil leak can be detected visually. A gas leak check will require a gas leak detector.

1. Blow shop air in the following locations for at least 15 seconds:

•	Behind the compressor clutch/pulley

•	In front of the compressor clutch/pulley

2. Probe the compressor area. If the detector goes to a solid alarm, a leak is present.

Tools Required

Notice: The tracer dye J 41447 was developed for use with the A/C Refrigerant 134a (R-134a) equipped vehicles or with vehicles that have been retrofitted from R-12 to R-134a. Do not use any other tracer dye in the R-134a system. Use of another dye may affect the system reliability and cause premature compressor failure. Use only a 1/4 oz. charge of the dye. Larger amounts may compromise the reliability of the A/C system. After adding the tracer dye, clean the service valves and all affected surfaces of the dye with GM Engine Degreaser GM P/N 1050436 or an equivalent in order to prevent a false diagnosis.

The R-134a refrigerant is uniquely different from the R-12 used in the past and may require additional methods for leak detection. The R-134a molecule is smaller than the R-12 molecule and can leak through smaller openings. R-134a also does not contain chlorine which was easily detected using the black light. The fluorescent leak detection method is meant to be used in conjunction with the electronic method, and will pinpoint smaller leaks. The R-134a dye takes time to work through the A/C system. Depending on the rate of the leak, the dye may take up to 7 days to become visible.