Audi S6 Ignition Switch Guide (1995-2004): Symptoms and Replacement
If your S6 has electrical gremlins or won't start, the ignition switch is a likely suspect.
- A bad ignition switch causes no-start conditions, stalling, and random electrical issues.
- This is a common failure on C4 and C5 Audis and is a manageable DIY replacement that does not require steering wheel removal.
- Before installing a new switch, you MUST verify the small actuator pin in the lock housing is in place to avoid breaking the new part.
- Do not drive a car with a faulty ignition switch, as it can stall unexpectedly in traffic.
Is Your Audi S6 Ignition Switch Failing?
A failing ignition switch in the 1995-2004 Audi S6 can cause a wide range of confusing electrical problems. Because this part controls power to nearly everything in the car, its failure can mimic other issues, like a dead battery or a bad starter. Symptoms often start intermittently and get worse, so it's important to recognize them early before you get stranded.
Key Differences: C4 vs. C5 Generation
The 1995-2004 range covers two distinct S6 models. The 1995 S6 belongs to the C4 platform, while the 2002-2003 S6 is on the C5 platform. While the replacement procedure is similar, the exact part number may differ. The C4 switch is part number 4A0 905 849 B, and the C5 switch is 4B0 905 849. Always verify the part for your specific year before ordering.
Known Issue: Wiring Harness Recall
NHTSA issued a recall for 1998-2004 Audi A6, S6, and Allroad models due to a wiring issue in the driver's side dashboard that could lead to an electrical short or fire. While not the ignition switch itself, this highlights the importance of inspecting the surrounding wiring for any signs of damage or previous repair when you replace the switch.
Choosing the Right Aftermarket Ignition Switch
You don't need to pay dealer prices for this part. Quality aftermarket options are available, but quality varies between brands. Here’s a breakdown of what to expect from the brands available for your S6.
| Brand Tier | Brands | Our Take |
|---|---|---|
| Premium Aftermarket | Standard Ignition (SMP), Vemo | Standard Ignition is a well-respected brand known for making reliable electrical components, sometimes even supplying the original parts to carmakers. Vemo is a German brand focused on European vehicles. Both are solid choices for a dependable, long-lasting repair. |
| Mid-Grade / OE-Style | Dorman, URO Parts | Dorman offers direct-fit parts that are widely available and often include design improvements over the original. URO Parts can be hit-or-miss with electronics; some users report premature failures, while others have no issues. For a critical part like an ignition switch, URO is a budget-conscious choice but may carry more risk than a premium brand. |
| Economy | Replacement | This is a generic or "white-box" brand. While it's the most affordable option, the quality and longevity are unpredictable. It can get your car running, but you might be doing the job again sooner than you'd like. |
Mechanic's Tip: Check the Actuator Pin!
A very common reason for new ignition switches failing right away on these Audis is a small metal actuator pin inside the lock housing falling out of place. When you remove the old switch, this pin can shift or drop. If you install the new switch without ensuring this pin is properly seated, it will break the new switch almost immediately. Before installing the new part, look into the housing and confirm the pin is present and moves freely when you turn the key mechanism.
Frequently Asked Questions (FAQ)
What's the difference between the ignition switch and the ignition lock cylinder?
This is the most common point of confusion. The ignition lock cylinder is the mechanical part you put your key into. The ignition switch is the separate electrical component mounted to the back of the lock cylinder housing. If your key is stuck or won't turn, the problem is likely the lock cylinder. If the key turns but the car won't start or has electrical issues, the problem is likely the ignition switch.
Is replacing the ignition switch a DIY job?
Yes, this is a very manageable DIY project for someone with basic tools and patience. It does not require removing the steering wheel or airbag, despite some official manuals saying so. The job involves removing the lower dash trim and instrument cluster to gain access. The switch itself is held by two small screws that often have red thread-locking compound on them, which you'll need to scrape off.
Do I need to reprogram my key after replacing the ignition switch?
No. The ignition switch is a simple electrical part and has no connection to the car's security or immobilizer system. You do not need to reprogram your key when replacing only the switch.
What are the most common mistakes when ordering this part?
The biggest mistake is confusing the switch with the lock cylinder and ordering the wrong part. Another common error is not verifying the part number for your specific year and model (C4 vs. C5). The 1995 S6 (C4) and 2002-2003 S6 (C5) use different switches.
Technical Specifications
OEM Part Numbers: 4A0905849B 4B0905849
This is the electrical switch portion only. It is located on the back of the ignition lock housing and is actuated by the lock cylinder.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Audi S6: