Mercedes Vito Viano W639 Headlight Switch Unit Button Knob A6399050000

The Mercedes Vito W639 Headlight Switch is an original part from the Switches, Control Elements, and Ignition Switches group, designed for precise control of the vehicle's front lighting system in a Mercedes brand vehicle. This used OEM component ensures factory-level compatibility with the electrical system, maintaining the correct operational logic for low beam, high beam, and parking lights.

Specifications and technical data

• SKU: A6399050000
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6399050000
• Substitutable numbers: A6399050000, A 639 905 00 00, BG
• Category: Switches & Controls

Function and Application of the Headlight Switch

The headlight switch in the Mercedes Vito W639 is responsible for operating the vehicle's basic external lighting modes. It is integrated with the electrical system to work with body control modules and the driver's signaling system. This provides the driver with clear, repeatable switching points and a stable electrical connection in every knob position.

This component is particularly important for:

• restoring full lighting system functionality after a factory switch failure,
• resolving issues with intermittent low or high beam lights caused by worn contacts,
• post-accident repairs where the lighting control panel has been damaged.

Construction and Integration with the Electrical System

The headlight switch in the Vito W639 is designed as a dashboard-mounted component with a factory connector matched to the vehicle's wiring harness. Its construction is based on a set of working contacts and a rotary mechanism that provides distinct, stepped switching positions. This makes operation intuitive and reduces the risk of accidentally engaging the wrong lighting mode.

Original manufacturing guarantees:

• correct fit for the mounting opening in the dashboard,
• proper interaction with factory indicator lights and signals on the instrument cluster,
• adequate mechanical resistance for daily use.

Benefits of Using an Original Used Part

Using an original, dismantled headlight switch maintains the integrity of the electrical system without requiring installation adaptations. In practice, this means:

• no need for wiring modifications or additional adapters,
• preservation of the switch's factory operating characteristics,
• better compliance with Mercedes service documentation and wiring diagrams.

This solution is particularly beneficial for servicing fleet vehicles and for repairs where consistency and predictability of the lighting system's operation are crucial.

Condition, Verification, and Selection by Part Numbers

The offered switch is part of the used original components group, allowing for a reasonable repair cost while maintaining manufacturer specifications. Before installation in the vehicle, it is recommended to verify compatibility using the OEM part number and interchangeable part numbers – this is the most reliable method to confirm compatibility with a specific Vito W639 equipment version.

If you want to learn more about safely using dismantled components in Mercedes cars and what to look for when choosing them, read the article Used Mercedes Parts – Original Components from Dismantling, which details the advantages of such solutions.

When selecting parts by OEM numbers, a practical guide on verifying part compatibility by manufacturer markings may also be useful – you can find it in the material Risk-Free Online Parts Shopping – How to Check Components by OEM Numbers.

Expanding the Control System in a Mercedes

When working on the lighting control system, it's worth taking a broader look at the group of components responsible for cabin functions. If you are planning a comprehensive repair or upgrade of the control area in your Mercedes and need other parts from the same group, such as additional switches, control modules, or ignition switch components, check the available parts in the Mercedes Switches, Control Elements, and Ignition Switches category.