For 1990-2009 cars

### Electronic Leak Detection Method

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:

• | A system indication of a low charge

• | After any service operation which disturbs the following items:

• | Components

• | Tubes

• | Connections

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:

• | One for R-134a

• | One for R-12

• | Gross

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:

• | Improper torque

• | Damaged O-rings

• | Lack of lubricant on the O-rings

• | Dirt/debris across an O-ring

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

• | Cotton gloves

• | Shop cloths

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

• | The scan rate

• | Carefully following the manufacturer's instructions regarding the following procedures:

- | Calibration

- | Operation

- | Maintenance

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:

• | Windshield washing solutions

• | Many solvents and cleaners

• | Some adhesives

Use care in order to prevent a false warning by ensuring that the surfaces are clean. Ensure that the surfaces are dry since the ingestion of liquids damages the detector. In order to ensure that no gasses are present that may cause a false warning, blow out the engine compartment using an air hose prior to the test.

Test the following areas using this procedure:

• | The pressure sensor (transducer)

• | The evaporator inlet and outlet

• | Other connections

• | All the brazed and welded areas

• | Areas showing signs of damage

• | Hose couplings

• | The compressor rear head and housing joints

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.

### Service Access Ports

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 cap is loose

• | The cap is missing

• | The wrong cap is used

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

### Evaporator Core

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.

### Compressor and Block Fitting

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.

### Fluorescent Leak Detection Method

#### Tools Required

• | J 41447 Florescent Tracer Dye

• | J 41459 R134a A/C Tracer Dye Injector

• | J 28428-E High Intensity Black Light

• | J 42220 Universal 12 V Leak Detection Lamp

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.