FAW Door Sill Trim Panel & Rails: 7 Critical MSUs for a Silent, Flawless Seal

Welcome to this in-depth technical analysis of the FAW Door Sill Trim Panel and Assembly Rail system. This is the complete, 7-type, multi-component assembly that forms the “lower half” of the ‘FAW Front Door’ (Assembly 683) on the FAW Jiefang CA4251P66K24T1A3E5 6×4 tractor. This is not just a cosmetic piece; it is a critical “logic” assembly with a dual function.

The “logic” of the FAW Door Sill Trim Panel system is twofold. First, it is the “Mechanical Logic” for the window, providing the rigid ‘Guide Rails’ and soft ‘Runnels’ that ensure the ‘Door Glass’ (Assembly 683, MSU 2) moves up and down smoothly, silently, and with a perfect seal. Second, it is the “NVH & Aesthetic Logic,” serving as the durable, visible trim panel that absorbs noise and gives the door its finished look.

This expert guide is essential for collision specialists and cab technicians. We will deconstruct the entire FAW Door Sill Trim Panel assembly into its 7 distinct Minimum Serviceable Unit (MSU) types. We will analyze the structural “guide rail” logic, the “sealing” logic of the runnels, the “acoustic” logic of the trim panel, and the critical “anti-vibration” fastener system.

Core 1: The “Structural Track” Logic (MSUs 1 & 4) (The “Longer” Module)

This group of MSUs forms the “skeleton” of the window lift mechanism inside the FAW Door Sill Trim Panel. This is the “logic” of precision movement, ensuring the heavy door glass moves perfectly vertically.

1. MSUs 1: ‘…Lower Guide Rail Assy’ (6101445-A01 / 6101450-A01)

These are the ‘Left/Right front door lower guide rail assy’. This is a critical structural MSU. Its “logic” is to provide the main *lower* anchor and track for the ‘Window Lifter Assy’ (Assembly 683, MSU 5). The lifter mechanism (whether electric or manual) must be bolted to a rigid, un-moving frame to provide the leverage needed to lift the heavy glass. This guide rail is that frame. It is precision-stamped from heavy-gauge steel and bolts directly to the ‘Welded Door’ (683) shell.

2. MSUs 4: ‘…Rear Guide Rail’ (6101481-A01 / 6101482-A01)

These are the ‘Left/Right front door rear guide rail’. This is the second half of the “track” logic. While MSU 1 is the *lower* track, this MSU is the *vertical rear* track.

The “logic” of this rail is to “capture” the rear roller of the window lifter mechanism. As the glass goes up, this rail ensures it travels in a perfectly straight, vertical line, *parallel* to the front guide rail (MSU 2). Without this “anti-bind” logic, the glass would “chatter” or “tilt” in its tracks, causing it to jam or shatter.

These two sets of rails (MSU 1 and MSU 4) work together to form the complete “guide logic” for the FAW Door Sill Trim Panel‘s window system. They are the primary MSUs replaced after a side-impact collision, as even a slight “bend” in these tracks will cause the window to fail. They are secured by the ‘Hexagon flange bolts’ (MSU 3).

Core 2: The “Silent Seal” Logic (MSUs 2 & 5)

This group of MSUs forms the “soft” interface for the window glass. This is the “sealing logic” of the FAW Door Sill Trim Panel system.

MSUs 2: ‘…Glass Front Runnel’ (6103053-A01 / 6103054-A01)

MSUs 5: ‘…Glass Rear Runnel’ (6103057-A01 / 6103058-A01)

These “runnels” (滑槽) are the “window channels” or “glass guides.” They are the U-shaped, EPDM rubber and “flocked” (fuzzy) channels that the ‘Door Glass’ (683) actually slides into. Their “logic” is threefold:

1. Sealing Logic: They create a 100% waterproof and windproof seal around the edges of the glass, preventing leaks and wind noise.

2. Low-Friction Logic: The “flocked” surface provides a soft, low-friction path for the glass, allowing it to slide easily and quietly, reducing the strain on the window lifter motor.

3. Anti-Rattle Logic: This is the “NVH logic.” The soft, compressive rubber holds the glass panel firmly, preventing it from “rattling” against the metal door frame when driving over rough roads. These are critical MSUs, as they wear out over time, leading to leaks, wind noise, and “rattly” windows.

Core 3: The “Aesthetic & NVH” Logic (MSU 6)

This component, the ‘Left/Right front door lower trim panel assy’ (6101515-D04 / 6101520-D04), is the primary “human-facing” MSU of the FAW Door Sill Trim Panel assembly.

Aesthetic Logic: This is the “finishing” logic. It is the large, molded polymer panel that the driver sees at the bottom of the door. It is designed to be durable, scuff-resistant, and easy to clean. It provides the “automotive-grade” finish, hiding the “guts” of the door (the metal shell, the ‘Waterproof Membrane’ (683), and the guide rails).

NVH Logic: This panel is also a key “acoustic” component. Its “logic” is to be the final “sound absorber.” It is often molded from a dense, “acoustically dead” polymer and may have a fibrous “shoddy” pad on its back. This “logic” is to absorb in-cab noise (like the radio) and block road/tire noise from “leaking” through the door.

Core 4: The “Dual-Fastener” Logic (MSUs 3 & 7)

The FAW Door Sill Trim Panel system uses two distinct fastener “logics” for its 20 total fasteners.

MSU 3: ‘Hexagon flange bolt’ (Q1840612F6) – Qty 8

This is the “Structural Logic” fastener. These 8 heavy-duty, high-tensile bolts are used for *metal-to-metal* connections. Their “logic” is to rigidly mount the structural ‘Guide Rails’ (MSUs 1 & 4) to the door’s steel ‘Welded Assy’ (683). The “flange” acts as a built-in lock washer, providing anti-vibration tension.

MSU 7: ‘…Combination screw’ (Q2360616F6) – Qty 12

This is the “Panel Logic” fastener. A “combination screw” has a captive lock washer. This “anti-vibration” logic is essential for mounting “soft” or “cosmetic” parts. These 12 screws are used to secure the ‘Trim Panel’ (MSU 6) and the ‘Runnels’ (MSUs 2 & 5) to their brackets, ensuring a tight, rattle-free fit.

FAW Door Sill Trim Panel & Rails Parts List

The following table provides the complete, detailed breakdown of all 7 component types identified in the FAW Door Sill Trim Panel and Assembly Rail system for the FAW CA4251P66K24T1A3E5 tractor.

Specifications

The specifications for the FAW Door Sill Trim Panel assembly are defined by its dual-function role as a structural guide rail system and an aesthetic/acoustic trim panel.