Info - Correct Diagnostic Procedure When Reviewing A/C Performance/Leak Suspected

This bulletin is being revised to update the text and model years. Please discard Corporate Bulletin Number 73-12-12A (Section 1 -- HVAC).

Important: The High Intensity Black Light, J 42220 or GM P/N 12377979, is the most up-to-date technology for finding extremely small leaks. Electronic leak detectors which do not use the heated diode sensor technology should not be used.

The following diagnostic procedure should be used when a poor A/c performance concern is being investigated and an A/C refrigerant leak is suspected:

1. Using the dealership's diagnostic computer, search the SI 2000 data base for bulletins applicable to the subject vehicle. A bulletin may have been issued changing the amount of refrigerant the system should contain and outline proper repair procedures.
2. Start the vehicle's engine and switch the A/C control to the maximum cold position.
3. Inspect the A/C compressor clutch (is it engaged). If the compressor is mounted in a hard-to-see location, switch the A/C system OFF and ON several times and listen for clutch engagement.
4. If the compressor clutch engages and stays engaged at idle, low side refrigerant pressure is sufficient to check for a leak.
5. To check for a leak, use Kent Moore Tool J 41459 for R134a and insert 1/4 oz of Kent Moore's J 41447 or GM P/N 12346303, R134a tracer dye, into the refrigerant system.

Important: By using this tool, the A/C refrigerant system does not have to be evacuated and/or opened just to insert the dye.

6. After insertion of the dye, spray a small amount of J 43872, fluorescent dye cleaner, around the low side fitting to remove any residue.
7. Observe and record on the repair order the ambient temperature and humidity as displayed on the ACR 2000, (J 43600) Air Conditioning Recovery, Evacuation and Charging System.
8. Place a dial thermometer (ie. J 23640, or J 6742-03) in the center A/C outlet duct..
9. Start and run the engine at 1500 RPM for 5 minutes with the A/C system in the maximum cold position.
10. At the end of the 5 minute run time, record the temperature displayed on the thermometer on the repair order.
11. If the center outlet temperature is at least 11° C (20° F) cooler than the ambient temperature, the system is performing as designed.
12. Use Kent Moore Tool J 42220 or GM P/N 12377979, ultraviolet leak detection lamp, and inspect the complete system for evidence of a leak.

Important: The leak dye mixes with the refrigerant lubrication (PAG oil). Therefore, extremely small leaks may be pressure, temperature or vibration sensitive and may not be active during the 5 minute test above. In this case, it may be necessary to request the vehicle be returned for further testing in 3 to 5 days. Vehicles which were driven in the rain, through sprinkler puddles, etc., may cause leak detection problems as the dye and the PAG oil are both water soluble.

For vehicles repaired under warranty, use:

Important: This labor operation has been revised and the 12 month limitation has been removed. If a second test with the black light is needed within 10 days, the Service Manager's approval will be required prior to submission of the claim. If a subsequent leak is found, the test would be considered part of the diagnostic time required for the repair.