2025-2026 Audi A5, S5, A6 Moisture in Footwell TSB 2079787/2

Revision History

This Technical Service Bulletin (TSB) 2079787/2 has undergone revisions since its initial publication. It was first released as Revision 1 on October 22, 2025. A subsequent Revision 2, with no specific date provided in the document, updated the header to include additional models and model years, ensuring broader applicability of the bulletin.

Symptoms

Owners of affected 2025-2026 Audi A5, S5, and A6 vehicles may experience noticeable issues related to moisture intrusion. The primary complaints include a distinct "musty or damp smell in the passenger compartment" and the presence of a "wet footwell in the front of the vehicle." These symptoms are a direct result of condensation leaking into the cabin. If you detect an "Audi A6 moisture in footwell" or an unusual odor, it indicates a potential problem that should be addressed to prevent further damage or mold growth.

Technical Background

Audi's Technical Service Bulletin (TSB) 2079787/2 identifies the root cause of the musty smell and wet footwell as an incorrect installation of the air conditioning unit's drain hose. This hose is designed to channel condensation from the AC system out of the vehicle. However, if it is not properly seated or installed, the condensation can leak directly into the passenger compartment. Over time, this continuous moisture accumulation saturates the vehicle's carpet in the footwell, creating a damp environment conducive to the development of a musty odor and potential mold.

Diagnosis and Documentation

When a customer reports a "musty or damp smell in the passenger compartment" or a "wet footwell in the front of the vehicle," technicians are instructed to first reproduce the complaint in the workshop to confirm the issue. Accurate documentation is crucial for addressing this concern, especially for warranty claims. Technicians must attach clear photographs to the DOC-IT system that unequivocally show the complaint. These images are required to include the vehicle's VIN and the date the photos were taken. It is critical that the photos are unedited, in focus, and taken with sufficient light, though high resolution is not a strict requirement. If necessary, technicians should mark the precise location of the problem within the images to provide a clear reference for parts analysis. Furthermore, photo documentation must strictly avoid showing any personal identifiers such as people, faces, license plates, or customer data to protect privacy.

Repair Procedure Summary

The repair procedure outlined in TSB 2079787/2 focuses on rectifying the improperly installed air conditioning drain hose. Technicians are directed to "Check and correct the position of the drain hose as shown in Figure 1." Figure 1, titled "Assembly overview for the Audi A5 and A6," visually depicts the correct routing and connection of the drain hose. The procedure involves inspecting the existing drain hose connection for the air conditioning unit, ensuring it is properly seated and sealed to prevent condensation from entering the passenger compartment. If the hose is found to be incorrectly positioned, it must be adjusted or reinstalled to its proper configuration as illustrated in the assembly overview. This ensures that all condensation drains effectively outside the vehicle, resolving the "Audi A6 moisture in footwell" issue and eliminating the musty smell. The TSB does not specify any special tools or part numbers for this correction, implying a repositioning or re-seating of the existing component.

Warranty Information

This Technical Service Bulletin, 2079787/2, provides specific guidelines for processing warranty claims related to the moisture issue. The designated Service Number for this repair is 8791, and the associated Damage Code is 0018. For labor operations, Audi specifies two options:

• Repair water drain hose – One side: This operation is identified by code 8791 4199 and is allocated 40 TU (Technical Units).
• Repair water drain hose – Both sides: This operation is identified by code 8791 4299 and is allocated 60 TU.

All warranty claims must be submitted in strict accordance with the Audi Warranty Policies and Procedures Manual and are subject to review or audit by Audi Warranty. The claim comment should reference "As per TSB 2079787/2." Importantly, if the vehicle is outside of its warranty period, this Technical Service Bulletin is explicitly stated to be "informational only." This means that repairs may not be covered by Audi. Any costs for drying or cleaning the vehicle's interior due to moisture are to be billed based on the time required, separate from the drain hose repair.

Important Warnings

Owners should be aware of several critical points regarding this Technical Service Bulletin 2079787/2. Firstly, if your 2025-2026 Audi A5, S5, or A6 is no longer covered by its factory warranty, this TSB is considered "informational only." This means that Audi may not cover the costs associated with diagnosing and repairing the moisture issue, including the labor for correcting the AC drain hose and any subsequent cleaning or drying of the vehicle's interior. It is crucial to consult with an authorized Audi dealer to understand your specific warranty coverage before proceeding with any repairs. Additionally, for any warranty claims, precise photo documentation is mandatory. Technicians are instructed to ensure these photos are unedited, in focus, and do not contain any personal information such as faces or license plates, to protect customer privacy and ensure claim validity.

Additional Information

All part and service references detailed within this Technical Service Bulletin 2079787/2 are subject to change or removal without prior notice. Technicians and owners should always verify the latest information and parts bulletins by consulting with their Audi Parts Department and/or the Electronic Parts Catalog (ETKA). Furthermore, it is essential to consult the official Repair Manual for specific details regarding fasteners, bolts, nuts, and screws that may require replacement during the repair process, ensuring proper reassembly and long-term durability of the fix.

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Source: NHTSA ID: 11028459