FAW Door Lock Mechanism: 9 Critical MSUs for a Secure, Flawless Cab

Welcome to this critical safety and security analysis of the FAW Door Lock Mechanism (Assembly 689). This is the complete, 9-component-type assembly that provides the “locking logic” for the ‘FAW Front Door’ (Assembly 683) on the FAW Jiefang CA4251P66K24T1A3E5 6×4 tractor. This is the core of the cab’s security, a “dual-logic” system that integrates mechanical security (keys, handles) with electronic security (power locks, remote control).

The FAW Door Lock Mechanism is a complex, high-stress assembly. Its “logic” is to provide a robust, multi-point interface for the driver. This includes the ‘Outer Handle’ (6105105-A01), the ‘Key Assy’ (6105190-A01), the ‘Inner Handle’ (6105075-B27-C00), the ‘Remote control lock mechanism’ (6105185-B27-C00), and the core ‘Lock Body’ (6105025-A01) itself. It is the “logic” that provides security against theft, safety against accidental opening, and the compression force needed for a quiet, weatherproof seal.

This in-depth guide is essential for technicians and collision repair specialists. We will deconstruct the entire FAW Door Lock Mechanism into its 9 distinct Minimum Serviceable Unit (MSU) types. We will analyze the “core latch” logic (MSU 1), the “exterior access” logic (MSUs 4 & 6), the “interior access” logic (MSU 8), the “remote” logic (MSU 7), and the critical “anti-vibration” fastener logic that secures this high-use system.

Core 1: The “Core Latch” Logic (MSU 1) (The “Longer” Module)

The heart of the FAW Door Lock Mechanism is MSU 1, the ‘Lock Body Assy’ (6105025-A01 / 6105030-A01). This is the heavy-duty, mechanical “rotary latch” that is mounted inside the ‘Welded Door’ (Assembly 683). Its “logic” is to securely “capture” the U-shaped striker pin on the cab’s B-pillar.

“Dual-Logic” (Manual vs. Electric): The parts list shows two distinct “logic” types for this MSU:

• Standard (-A01): This is the purely mechanical version. It is actuated *only* by mechanical rods/cables connected to the inner (MSU 8) and outer (MSU 4) handles.
• Electric (-AA01): This is the “power lock” version. It contains the *exact same* mechanical latch but adds an integrated 24V DC motor (an “actuator”).

“Actuator Logic”: The “electric” (AA01) version is the “logic” that enables all advanced features. This actuator receives low-voltage signals from the ‘Remote control lock mechanism’ (MSU 7) or the ‘Door Controller’ (Assembly 588).

When you press the “lock” button on the key fob or the ‘Door Trim’ (685), this MSU’s “logic” is to *move a cam* that physically *disconnects* the ‘Outer Handle’ (MSU 4) from the latch mechanism. The handle will still pull, but it will be “dead,” preventing theft. The “unlock” signal reverses this, re-engaging the handle. This “logic” of disconnecting the handle, rather than blocking the latch, is a robust, modern security design.

Serviceability (MSU): The ‘Lock Body’ is a sealed, greased-for-life MSU. It is not repaired. It is a high-wear component, and failures are common (broken internal springs, seized mechanism). This MSU is replaced as a single unit, and is secured by the ‘Combination screws’ (MSU 5 or 9).

Core 2: The “Exterior HMI” Logic (MSUs 4 & 6)

This group of MSUs forms the “exterior access” for the FAW Door Lock Mechanism.

MSU 4: ‘…Outer Handle Assy’ (6105105-A01 / 6105110-A01): This is the “pull-to-open” logic. It is a high-strength, ergonomic handle (Left & Right) that provides the *mechanical leverage* to actuate the ‘Lock Body’ (MSU 1).

This MSU is designed for durability (to withstand millions of cycles and the pull of a driver) and aerodynamics (to sit flush with the ‘FAW Front Door’ (683) skin, reducing drag). It is a critical MSU that is secured by the high-strength screw-and-washer system (MSUs 2 & 3).

MSU 6: ‘Key assy’ (6105190-A01): This is the “manual security” logic. The parts list calls for two (2), one for each door. This is the physical key cylinder. Its “logic” is to provide a mechanical “override” for the *electric* lock system. If the truck’s battery is dead, this key is the *only* way to bypass the “locked” actuator and gain entry. This MSU is a high-security component, designed to resist picking and drilling.

Core 3: The “Interior HMI” & “Remote” Logic (MSUs 8 & 7)

This group represents the “convenience” and “electronic” logic of the FAW Door Lock Mechanism.

MSU 8: ‘…Inner Handle Assy’ (6105075-B27-C00 / 6105080-B27-C00): This is the “interior release” logic. It is the “pull-handle” located on the ‘Door Trim’ (Assembly 685). This MSU connects via a rod or cable to the ‘Lock Body’ (MSU 1). Its “logic” is to *always* be connected, providing a “panic-proof” exit. Even if the door is *electrically* locked, pulling this handle *mechanically* bypasses the lock and opens the door.

MSU 7: ‘Remote control lock mechanism’ (6105185-B27-C00): This is the “brain” of the *remote* system. This is the Radio Frequency (RF) receiver. Its “logic” is to “listen” for the “lock/unlock” signal from the driver’s ‘Remote Control Assy’ (the key fob, Assembly 588).

When this MSU receives a valid, encrypted “rolling code” signal, it provides the “logic” to the ‘Door Controller’ (588), which then sends the 24V “lock” or “unlock” pulse to the ‘Electric Lock Body’ (MSU 1, AA01). This is the core MSU for all “keyless entry” logic.

Core 4: The “Vibration-Proof” Fastener Logic (MSUs 2, 3, 5, 9)

The FAW Door Lock Mechanism is a high-use, high-vibration system. The fastener “logic” is critical for safety and NVH.

MSUs 2 & 3: ‘Screw’ (Q2540612) & ‘…Lock Washer’ (Q41406) – Qty 6 (each): This is the “high-strength” logic. The ‘Outer Handle’ (MSU 4) is under constant *pulling* (tensile) force. This system uses a separate bolt and a ‘taper pin lock washer’. This “logic” provides the strongest possible, non-loosening grip for this high-stress MSU.

MSUs 5 & 9: ‘…Combination screw’ (Q2360612) – Qty 10 total: This is the “anti-rattle” logic. These are used to mount the *internal* components: the ‘Lock Body’ (MSU 1) and the ‘Inner Handle’ (MSU 8).

The “Combination” (组合) logic is that these screws have a *captive, pre-attached lock washer*. This is essential for a “blind” installation inside a door. It ensures that the anti-vibration lock washer cannot be forgotten or dropped, guaranteeing a silent, rattle-free installation that will not shake loose over time.

FAW Door Lock Mechanism Parts List & Specifications

The following table provides the complete, detailed breakdown of all 9 component types identified in the FAW Door Lock Mechanism assembly for the FAW CA4251P66K24T1A3E5 tractor.

Specifications

The specifications for the FAW Door Lock Mechanism are defined by its function as a multi-part, hybrid (mechanical/electric) security and access system.