BMW F44 Gran Coupé Door Window Lifter Regulator Motor Rear Left N/S 9851139

BMW F44 Gran Coupé Door Window Lifter Regulator Motor Rear Left N/S is an original component from the Window Regulators and Motors group, designed for the rear left window in the Gran Coupé body style. It ensures stable window guidance, proper operation of the lifting and lowering mechanism, and maintains the factory functionality of the door.

Specifications and technical data

• SKU: 9851139
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 9851139
• Substitutable numbers: 9851139, 4876379, 51354876379
• Location on the vehicle: Rear, Left
• Category: Window Motors & Regulators

Purpose and function in the vehicle

The presented window regulator is designed for installation in the rear left door of the BMW F44 Gran Coupé. It is responsible for the precise guidance of the window within the tracks and the transmission of power from the window control system, which translates into smooth and repeatable operation of the entire mechanism.

Its placement in the rear part of the vehicle body makes this component significant for both passenger comfort and the sealing and acoustics of the interior. A fully functional regulator reduces the risk of jamming, uneven window closing, or excessive play in the mechanism.

Benefits of using an original window regulator

Using an original solution from the BMW range allows for maintaining the factory performance parameters of the window mechanism. Key advantages include:

• Precise fit for the rear left door – compatibility with the panel construction, guides, and mounting points.
• Stable cooperation with the factory window control system and other door components.
• Reduction of the risk of improper window closing and associated leaks.
• The ability to restore proper window operation after damage or wear of the previous mechanism.

Thanks to the preservation of the original geometry and mounting points, the installation process is straightforward, without the need for modifying the door structure or additional component adjustments.

Installation and operational characteristics

The regulator is intended for installation in the factory mounting points in the rear left door. The design, specifically for the BMW F44 Gran Coupé model, facilitates servicing and reduces replacement time compared to universal solutions.

After correct installation, the mechanism works with the existing electrical harness and window control, which allows for maintaining the vehicle's original functionality. This is particularly important in vehicles equipped with advanced comfort systems, where proper window operation also affects the performance of the central locking and safety features.

Condition and service application

The item comes from a used vehicle, making it an attractive cost-effective alternative to new parts while maintaining original BMW specifications. Such components are frequently used in professional workshops and for post-accident repairs, where combining technical compatibility with a rational budget is key.

The regulator will prove useful both for the typical replacement of a worn-out mechanism and for door restoration after mechanical damage, ensuring the restoration of proper window operation in the rear left part of the body.

If you are planning a comprehensive repair or upgrade of the door and side window area in your BMW and need other components from the same group, such as guides, lifting mechanisms, or window drives, check out the available parts in the BMW Window Regulators and Motors category.

Part selection by numbers and technical support

When selecting components such as window regulators, it is crucial to verify compatibility by part number or interchangeable numbers, as well as by the specific vehicle data. In service practice, identification by VIN and comparing markings on the removed component is often used to avoid problems with installation and mechanism operation.

If you want to better understand what the professional process of selecting used components based on OEM numbers looks like and what the real economic benefits of choosing parts from the secondary market are, it is worth reading the guide Why it is worth buying used gearboxes and engines – facts instead of myths, which describes identification procedures by numbers and cost ratios compared to new components.