Audi A6, A7, A8 & S8 Tail Light Failure (2008-2015): A Guide to Water Leaks, LED Problems, and Part Numbers

Critical Compatibility Warning: Not All Tail Lights Are the Same

Before purchasing a replacement, identify your vehicle's platform from the table below to find the correct part number series.

Note: This guide covers the outer tail light that mounts on the quarter panel, not the inner light mounted on the trunk lid.

Symptoms of Tail Light Failure

A failing Audi tail light will usually make itself known in several ways. You may experience one or more of the following issues:

• Dashboard Warning Light: The most common sign is a "Bulb Out" or similar warning message appearing on your instrument cluster.
• Flickering or Dim LEDs: Sections of the tail light may flicker, appear dim, or work intermittently. This can happen when driving or even when the car is off.
• Partial or Complete Failure: One function may stop working (like the brake light), while others continue to operate. Eventually, the entire unit may go dark.
• Rapid Blinking Turn Signal: When a turn signal LED fails, the indicator on your dashboard may blink much faster than normal.
• Condensation or Water Inside: You may see fog, condensation, or even visible water droplets collected inside the tail light lens. This is a sure sign the seals have failed.

The Real Cause: Water Intrusion and Corrosion

The number one cause of failure for these LED tail lights is water getting inside the housing. Over time, the foam or rubber gaskets that seal the light assembly against the car's body dry out, shrink, and crack. It's also possible for hairline cracks to form in the plastic housing itself, often too small to see easily.

Once moisture gets in, it collects on the internal circuit boards that control the LEDs. This leads to corrosion on the electronic components and connector pins, causing short circuits and electrical faults. 🎬 See how to solve tail light moisture and condensation issues At first, this might just cause a flicker, but over time, the corrosion will destroy the circuitry and cause a permanent failure. In forum discussions, owners frequently report that hitting the light can make it temporarily work again, which points to a bad connection caused by this internal corrosion.

Buying a Used Tail Light: What to Check

Since a new OEM tail light can be extremely expensive, a quality used OEM part is often the best value. However, you must inspect it carefully to avoid buying a part that is already failing.

1. Verify the Part Number

This is the most important step. The part number is printed on a sticker or molded into the plastic on the back of the tail light housing. It must exactly match the part number on your old light. Do not rely on visual appearance alone.

2. Inspect the Lens and Housing

Check the entire unit for cracks. Pay close attention to the edges and corners. Even a tiny hairline crack is a path for water to enter. Reject any light with visible cracks in the lens or the black plastic housing.

3. Check for Signs of Water

Hold the light up and look for a "water line" or hazy film on the inside of the lens. This indicates it has had water inside before and is likely compromised. A used light should be perfectly clear and dry inside.

4. Examine the Mounting Points and Seals

Ensure all plastic mounting tabs and studs are intact and not cracked or repaired. Check the condition of the foam gasket on the back. While it's wise to install a new gasket anyway, a crumbling or flattened original gasket suggests a hard life.

5. Inspect the Electrical Connector

Look at the pins inside the electrical connector socket. They should be clean and shiny. Any green or white crusty buildup is a sign of corrosion from water damage, and you should not buy the part.

Known Issues and Vehicle-Specific Information

2008-2010 Audi A8 / S8 (D3 Platform)

• Common Issue: These facelift models were among the first with full LED tails, and failures from water ingress are common. Some owners with electronics skills have successfully repaired the internal boards, but it requires soldering and is not a simple task.
🎬 Watch this guide on repairing D3 tail light water leaks
• Compatibility Note: For the 2008 model year, a change was made mid-production. This part fits vehicles from VIN 4E-8-002001 onwards. Verify your VIN before ordering.
• Known Part Numbers: 4E0945095J, 4E0945095P (Left); 4E0945096J, 4E0945096N (Right).

2011-2015 Audi A8 / A8 Quattro / S8 (D4 Platform)

• Common Issue: Like the D3, these lights are prone to seal failure and internal moisture damage over time, leading to LED segments failing. The units are sealed and not considered serviceable.
• Known Part Numbers: 4H0945095, 4H0945095A, 4H0945095E, 4H0945095K (Left); 4H0945096A (Right).

2012-2015 A6 / A7 / S6 / S7 / RS7 (C7 Platform)

• Common Issue: Water leaks are also the main culprit on the C7 platform. Models with the optional dynamic 'sweeping' turn signals have an additional control module that can fail, causing the animation to glitch or stop. Sometimes this can be fixed with a software update, but often requires replacing the entire light assembly.
• Aftermarket Warning: Owners who install cheap aftermarket tail lights on these models often report flickering or immediate "bulb out" errors. This is because the car's computer expects a specific electrical resistance from the OEM unit, and the aftermarket parts don't match it, triggering a fault.
• Known Part Numbers (A6/S6): 4G5945095B (Left); 4G5945096B (Right).
• Known Part Numbers (A7/S7/RS7): Part numbers will start with 4G8. The shape is different from the A6/S6.

Replacement Difficulty: 2/5

Replacing the outer tail light is a straightforward DIY job that usually takes less than 30 minutes per side.

1. Open the Trunk: Access the area behind the tail light.
2. Remove Trim: Pull back the trunk liner or remove a small plastic access panel to expose the back of the light assembly.
3. Unplug Connector: Depress the tab on the single electrical harness connector and pull it off.
4. Remove Nuts: Using a socket wrench (typically 10mm), remove the two or three nuts holding the assembly in place.
5. Remove Assembly: Gently pull the tail light straight back out of the quarter panel.
6. Install New Unit: Installation is the reverse of removal. Hand-tighten the nuts to avoid cracking the plastic, then test all light functions before reinstalling the trim.

Cost of Replacement

The cost can vary dramatically depending on the source of the part.

Frequently Asked Questions (FAQ)