2018-2024 Audi AC Cooling Insufficient TSB 2064077/4

Audi Technical Service Bulletin (TSB) 2064077/4, issued on March 29, 2024, provides an updated diagnostic method for identifying refrigerant leaks in vehicles equipped with R134a or R1234yf air conditioning systems. This bulletin supersedes TSB Group 87 number 23-60, dated October 23, 2023, for reasons related to updated warranty information and model year coverage. It is crucial for addressing instances where the cabin air conditioning cooling capacity is insufficient or without function.

Revision History

This Technical Service Bulletin has undergone several revisions to ensure accuracy and comprehensive coverage:

• Revision 4 (March 29, 2024): The header was revised to remove Model Year 2018 A8, and warranty information was updated, specifically removing GFF allowance restrictions for BEV and PHEV vehicles.
• Revision 3 (October 23, 2023): Warranty details were revised to add GFF allowance for BEV and PHEV vehicles.
• Revision 2 (August 18, 2023): The header was revised to add Model Year 2024, service procedures were updated to include a relay and fuse carrier suggestion, and a warranty table was added.

Symptoms of Insufficient AC Cooling

Owners may notice that their vehicle's air conditioning system is not cooling the cabin effectively or has stopped functioning entirely. This condition, often described as Audi AC cooling insufficient, typically points to a refrigerant leak within the system. The official condition states: "The cabin air conditioning cooling capacity is insufficient or without function on an R134a or R1234yf refrigerant system equipped vehicle."

Technical Background

Traditionally, diagnosing refrigerant circuit leaks has relied on methods like adding contrast dye with UV light inspection, using electronic halogen leak detectors, or pressurizing the circuit with nitrogen and applying soap and water to detect bubbles. However, these methods have proven unreliable, especially when diagnosing leaks in hard-to-access areas such as the evaporator core. False-positive readings from halogen leak detectors are common, and visual inspection of the evaporator core is problematic due to its concealed location.

New Diagnostic Method for Refrigerant Leaks

To accurately pinpoint refrigerant leaks, Audi has introduced an additional diagnostic method utilizing calibration gas (a mixture of 95% nitrogen and 5% hydrogen) and a specialized electronic hydrogen detector, the VAS523003A. This method is particularly effective for diagnosing leaks in areas that are difficult to access, such as the evaporator core concealed within its housing. The new procedure, detailed in TSB 2064077/4, is designed to provide more precise and reliable leak detection compared to older techniques.

For the newer R744 refrigerant system found in the Q4 e-tron, a similar leak detection method using calibration gas is required, as additives cannot be used. The AT-448 Tool Set, originally released for the R744 system, can be adapted to diagnose R134a and R1234yf refrigerant circuit leaks as well. However, it is important to note that while the diagnostic method for the R744 system in the Q4 e-tron is similar, there are important differences in the procedure and, as such, should be carried out using the procedure in ElsaPro.

Important Warnings and Notices

Several critical warnings are highlighted in TSB 2064077/4 to ensure safety and prevent damage during the diagnostic process:

• Flammable Gas Hazard: "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."
• High Voltage Safety: "DANGER 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 de-energize the high-voltage system." This warning applies when servicing a high voltage vehicle and is repeated for both initial de-energization and re-energization of the vehicle.
• AC System Operation: "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. 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."
• Q5 Evaporator Replacement Specific: "Should the evaporator for the Q5 be confirmed leaking by way of this diagnostic procedure and replacement of the evaporator is performed it is necessary to loosen and refasten the Relay and Fuse Carrier 3 -SR3- (shown in figure 8, position 1) in the course of the repair. During reassembly of the vehicle 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."

Detailed Repair Procedure

If your Audi is experiencing Audi AC cooling insufficient performance, the following diagnostic steps are to be performed by a qualified technician:

1. Refrigerant Recovery: If the vehicle arrives with insufficient cabin cooling, recover any remaining refrigerant from the air conditioning system. Compare the recovered amount to the specified volume; a significantly lesser amount (more than 50% lost) indicates an active refrigerant circuit leak.
2. Calibration Gas Acquisition: Obtain a tank of calibration gas, which is a mixture of 95% nitrogen and 5% hydrogen. This gas must be sourced locally from suppliers like Airgas®. Figure 1 in the TSB illustrates a typical calibration gas cylinder.
3. Pressure Regulator Connection: The pressure regulator included in the NITROKITG is not suitable for flammable gases. Instead, use the VAS 584005 pressure regulator, which is part of the AT-448 Tool Set and designed for flammable components. Connect the VAS 584005 pressure regulator to the calibration gas tank, ensuring the tank valve remains closed. Figure 2 shows the VAS 584005 pressure regulator attached to the tank.
4. Vehicle Preparation: Set the HVAC settings to full defrost, close all instrument panel vents, and ensure the fresh air intake is closed (recirculation mode). Completely seal off the cabin by closing windows, sunroof, doors, and the rear lid. Turn off the vehicle, ensuring the key is off and no blower is activated.
5. High Voltage De-energization: If servicing a high voltage vehicle, an Audi high-voltage technician or expert must de-energize the high-voltage system.
6. NITROKITG Connection: Connect the appropriate service hose and high side service port snap coupler from the NITROKITG (for either R134a or R1234yf systems) to the vehicle's refrigerant circuit.
7. System Evacuation and Manifold Connection: Evacuate the vehicle's refrigerant circuit for 15 minutes. Once the circuit is free of refrigerant, connect the service manifold from the NITROKITG Automotive A/C Nitrogen Leak Test Kit to the high side service port. Figure 3 shows the NITROKITG manifold connected to the high side service port. Only one port needs to be connected for this diagnosis, as shown in Figure 4.
8. Charging with Calibration Gas: Connect the VAS 584005 Pressure Reducer to the NITROKITG manifold. Fill the refrigerant circuit with calibration gas to an absolute pressure of no greater than 14 bar. Figure 5 illustrates the calibration gas pressure in the circuit.
9. Equalization Period: Allow the circuit pressure to equalize for 20 minutes before proceeding with leak detection.
10. Leak Detection Preparation: Close off the defroster outlets with masking tape, leaving a small opening for the VAS 523003A gas leak detector probe. Figure 6 shows the detector in place in the defroster outlet.
11. Performing Leak Diagnosis: The VAS 523003A gas leak detector reacts to the hydrogen component of the calibration gas. Since hydrogen is lighter than air, it will rise to the position of the detector probe. The hydrogen content in the calibration gas evaporates after a short period. Therefore, perform the leak diagnosis immediately after charging the refrigerant circuit and the 20-minute equalization period. Depending on conditions, recharging the circuit with calibration gas may be necessary for clear identification of an evaporator core leak. Figure 7 shows the VAS 523003A in the defroster outlet detecting hydrogen.
12. Evaporator Core Assessment: If no leak is detected through the defroster outlet using this method, the evaporator core is not the source of the refrigerant leak and should not be replaced. Continue diagnosis using the VAS 523003A on all other components of the refrigerant circuit to determine the source of the leak.
13. Post-Diagnosis: Once all leak sources are identified, close the valve on the calibration gas tank. Slowly ventilate any remaining calibration gas until the circuit pressure equalizes with atmospheric pressure. Proceed with necessary repairs, evacuate the refrigerant circuit, and recharge the system.
14. Q5 Specific Reassembly: For Audi Q5 models, if the evaporator is replaced, it is critical to loosen and refasten the Relay and Fuse Carrier 3 -SR3- precisely in its original position during reassembly. Failure to do so can lead to water intrusion and subsequent component damage. Figure 8 shows the Relay and Fuse Carrier 3 -SR3-.
15. High Voltage Re-energization: When re-energizing a high voltage vehicle, an Audi high-voltage technician or expert must bring the high-voltage system back into service.

Required Tools and Parts

To perform this diagnostic and repair procedure, specific tools are required:

• VAS581009: R744 CO2 A/C Service Unit
• VAS584005: Pressure Reducer and Hose
• NITROKITG: Automotive A/C Nitrogen Leak Test Kit
• VAS523003A: Gas Leak Detector

Warranty Information

Warranty claims submitted for payment must adhere to the Audi Warranty Policies and Procedures Manual. Claims are subject to review or audit by Audi Warranty. The relevant details are:

• Claim Type: 110 (Up to 48 Months/50,000 Miles) or G10 (for CPO Covered Vehicles - verify owner). If the vehicle is outside of any warranty, this Technical Service Bulletin is informational only.
• Service Number: 8760
• Damage Code: 0050
• Labor Operations:
  • Evaporator remove and reinstall (All models except e-tron GT): 8760 1950 (See SRT with associated operations)
  • Heating, ventilation unit remove and reinstall (e-tron GT): 8515 1950 (See SRT with associated operations)
  • Air conditioner check: 8760 0199 (Time necessary for diagnosis supported by punch time, Max 130 TU)
• Diagnostic Time: GFF 0150 0000 (Time stated on the diagnostic protocol, Max 50 TU)
• Road Test Prior to Service Procedure: No allowance (0 TU)
• Road Test After Service Procedure: No allowance (0 TU)
• Claim Comment: As per TSB 2064077/5

NHTSA ID: 2064077/4