Mercedes Vito Viano W639 Headlight Switch Button Knob Unit A6399050000

Visual condition of the part 

The product shows signs of use visible in the photos. 

Mercedes Vito Viano W639 Headlight Switch Button Knob Unit is a factory-fitted lighting control component designed for commercial and passenger models of this series. It offers precise, mechanical light control from the dashboard, maintaining the original cockpit ergonomics. This is a practical solution for drivers who want to restore full functionality to the lighting system using an original Mercedes brand switch in used condition.

Specifications and technical data

• SKU: A6399050000-3
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6399050000
• Substitutable numbers: A6399050000, A 639 905 00 00
• Category: Switches & Controls

Function and application of the headlight switch

The headlight switch in Vito and Viano W639 models is responsible for operating the vehicle's basic lighting modes via a single, convenient knob. This component is integrated into the vehicle's electrical system and works with the factory lighting setup, ensuring consistent operation with other control modules in the cabin.

By using an original component, the correct operating characteristics of the knob, tactile switching positions, and compatibility with factory wiring and dashboard connectors are maintained.

Construction and ergonomics of the control element

The switch belongs to the Switches, control elements and ignition locks group, meaning it is designed as an integral part of the cabin control panel. The knob is shaped to match the interior design of the Vito and Viano W639, and its construction allows for intuitive operation without taking your eyes off the road.

The layout of the operating positions and the way the rotary mechanism works are in accordance with the manufacturer's standard, which makes it easier for the driver to quickly switch lighting modes even when wearing work gloves or driving at night. Using an original solution reduces the risk of loose knobs and incorrect headlight activation.

Benefits of using an original Mercedes switch

Choosing a headlight switch dedicated to the Vito and Viano W639 allows you to maintain the consistency of the electrical system and avoid problems typical of aftermarket replacements. Key advantages include:

• maintaining the factory logic of light operation and instrument cluster signaling,
• secure fit to the dashboard panel without the need for modifications,
• compatibility with the wiring harness and connectors provided by the manufacturer,
• consistent interior aesthetics, with no differences in texture or shape of the control element.

For vehicles used intensively – both in commercial and passenger applications – using an original switch reduces the risk of failures resulting from inaccurate fitment or incorrect electrical parameters.

Used condition and installation aspects

The offered item is in used condition, which in practice means it has been removed from a vehicle and was previously in operation. This type of part is a good solution for repairs where maintaining the original specification while optimizing service costs is important.

The switch is designed for installation in place of the factory component, using existing mounts and connectors. In most cases, installation is limited to removing the panel, unplugging the old switch, and plugging in the new one, without the need to interfere with the wiring harness. It is recommended that the installation be performed by a person with experience in electrical systems in Mercedes vehicles, which will help avoid damage to the panel and connectors.

Expansion of the control system and additional materials

If you are planning a comprehensive repair or upgrade of the cockpit area in your Mercedes and need other elements from the same group, such as additional switches, control elements, or ignition lock modules, check out the available parts in the Mercedes switches, control elements and ignition locks category.

When performing service work on the electrical and control system, it is also worth paying attention to the condition of the systems responsible for driving safety. For vehicles where you are simultaneously servicing the braking system, a guide material describing the selection of used components may be helpful – you can find detailed tips in the article Second-hand braking system: how to safely choose discs, calipers, and ABS?.