2022-2024 Audi AC Refrigerant Leak Diagnostic TSB

Symptoms

Owners may experience the following issues with their vehicle's air conditioning system:

• Insufficient cabin cooling capacity.
• The air conditioning system is without function.

These symptoms often point to a refrigerant circuit leak, which this Technical Service Bulletin (TSB) aims to help diagnose more effectively, especially for an Audi AC refrigerant leak.

Diagnosis / Trigger Conditions

Traditionally, diagnosing refrigerant circuit leaks involved adding contrast dye, using electronic halogen leak detectors, or applying soap solutions. However, these methods can be unreliable, particularly when trying to detect a leak in the evaporator core, which is concealed and difficult to access. False-positive readings are common with halogen detectors for evaporator core leaks.

This TSB introduces an additional diagnostic method using calibration gas (a mixture of 95% nitrogen and 5% hydrogen) and an electronic hydrogen detector (VAS523003A). This method is more effective for diagnosing leaks in hard-to-reach areas of the refrigerant circuit, such as the evaporator core. A significantly lesser amount of refrigerant recovered (more than 50% of the total volume lost) indicates an active Audi AC refrigerant leak.

Important Warnings

Audi has issued several critical warnings regarding the diagnostic procedure outlined in this TSB:

• Calibration Gas Handling: "Extreme caution must be exercised when handling and using calibration gas. The hydrogen component of the gas mixture is flammable. Failure to employ proper handling and use protocol invites the risk of serious personal injury or death."
• AC System Activation: "The air conditioning system must not be activated while the circuit is charged with calibration gas. Running the air conditioning system while it is charged with calibration gas will damage the compressor."
• Vehicle Operation: "If necessary apply a warning sign to the vehicle stating “Do Not Run” or a similar warning to prevent accidental operation while the circuit is filled with calibration gas for the purposes of diagnosis."
• High Voltage Systems: "High voltage increases the risk of fatal injury. Severe bodily injury or death by electrocution or electric arcs is possible. Have an Audi high-voltage technician or an Audi high-voltage expert bring the high-voltage system back into service."
• Q5 Evaporator Replacement: If replacing the evaporator in a Q5, it is "critically important that this relay and fuse carrier in particular be reinstalled in its correct original position. Failure to reinstall the Relay and Fuse Carrier 3 precisely will result in water intrusion and subsequent component damage."

Repair Procedure Summary

This TSB outlines a detailed procedure for diagnosing an Audi AC refrigerant leak using calibration gas. The process involves several steps:

1. Refrigerant Recovery: If the vehicle exhibits insufficient cooling, recover the remaining refrigerant and compare the amount to the specified volume. A significant loss indicates an active leak.
2. Calibration Gas Preparation: Obtain a tank of calibration gas (95% nitrogen / 5% hydrogen) from a local supplier (e.g., Airgas®).
3. Pressure Regulator Connection: Connect the VAS 584005 pressure regulator to the calibration gas tank. Ensure the tank valve remains closed initially.
4. HVAC System Setup: Set the HVAC system to full defrost, close all instrument panel vents, and ensure the fresh air intake is in recirculation mode. Completely close the cabin (windows, sunroof, doors, rear lid) and turn off the vehicle (key off, no blower activation).
5. High Voltage De-energization: For high voltage vehicles, de-energize the high voltage system before proceeding.
6. Circuit Connection: Use the NITROKITG service hose and the appropriate high side service port snap coupler for either R134a or R1234yf refrigerant systems to connect to the vehicle's refrigerant circuit.
7. Circuit Evacuation: Evacuate the vehicle's refrigerant circuit for 15 minutes to ensure it is free of refrigerant.
8. Calibration Gas Charging: Connect the VAS 584005 Pressure Reducer to the NITROKITG manifold and fill the circuit with calibration gas to an absolute pressure of no greater than 14 bar.
9. Equalization Period: Allow the circuit pressure to equalize for 20 minutes before starting leak detection.
10. Leak Detection: Begin leak detection using the VAS 523003A gas leak detector. Start by closing off defroster outlets with masking tape, leaving a small opening for the detector probe. The detector reacts to the hydrogen component of the calibration gas.
11. Further Diagnosis: If no leak is detected through the defroster outlet, the evaporator core is not the source of the leak and should not be replaced. Continue diagnosis on all other components of the refrigerant circuit.
12. Post-Diagnosis: Once all leak sources are identified, close the calibration gas tank valve. Slowly ventilate any remaining calibration gas until the circuit pressure equalizes with atmospheric pressure. Then, proceed with necessary repairs, evacuate the refrigerant circuit, and recharge the system.
13. Q5 Specific Note: If an evaporator replacement is performed on a Q5, ensure the Relay and Fuse Carrier 3 -SR3- is correctly reinstalled to prevent water intrusion and component damage.
14. High Voltage Re-energization: If applicable, have an Audi high-voltage technician or expert re-energize the high-voltage system.

Required Tools or Parts

Technicians will require specific tools for this diagnostic procedure:

• VAS581009: R744 CO2 A/C Service Unit (though the TSB focuses on R134a/R1234yf, this unit is mentioned in the context of the AT-448 Tool Set for R744 systems, which can be adapted).
• VAS584005: Pressure Reducer and Hose (suitable for flammable components).
• NITROKITG: Automotive A/C Nitrogen Leak Test Kit (includes service hose and high side service port snap coupler).
• VAS523003A: Gas Leak Detector.
• Calibration Gas: A tank of 95% nitrogen / 5% hydrogen, to be sourced locally (e.g., Airgas®).

Warranty Information

Warranty claims for this procedure are subject to the following conditions:

• Coverage is typically for 110 up to 48 Months/50,000 Miles.
• For Certified Pre-Owned (CPO) vehicles, use claim type G10 and verify owner eligibility.
• If the vehicle is outside of any warranty, this Technical Service Bulletin is for informational purposes only, and the repair will not be covered under warranty.
• All warranty claims must comply with the Audi Warranty Policies and Procedures Manual.

Superseded Bulletin

This Technical Service Bulletin, 2064077/2, dated August 18, 2023, supersedes Technical Service Bulletin Group 87 number 22-24 dated April 15, 2022. The revision includes adding Model Year 2024 to the header, suggestions for relay and fuse carrier, and an updated warranty table.