FAW Cab Tilt Control Unit: The 2-in-1 “Dual-Logic” System for Total Cab Access

Welcome to this in-depth technical breakdown of the FAW Cab Tilt Control Unit. This is the complete hydraulic and electric assembly responsible for lifting the entire cab-over-engine on the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This is one of the most critical safety and maintenance systems on the vehicle, as its “logic” is to provide technicians with safe, reliable access to the engine and transmission.

The “Logic Assembly” designation for the FAW Cab Tilt Control Unit is key. This is not one system, but a “dual-logic” or “hybrid” system. It combines a primary ‘Electric pump assy’ (5002075B91W-C00) for effortless, push-button operation, with a secondary, “backup” ‘Manual pump assy’ (5002070B91W-C00). This built-in redundancy is a critical safety “logic,” ensuring that a technician can *always* lift the cab, even if the truck’s battery is dead.

This expert guide is an essential resource for technicians and fleet operators. We will deconstruct the entire FAW Cab Tilt Control Unit into its 23 component types. We will analyze the “Electric Logic” (the motor, pump, and relay), the “Manual Logic” (the hand pump and switch), the shared “Hydraulic Network” (the hoses), and the “Fastening Logic” (the critical anti-vibration hardware).

Core 1: The “Electric Logic” System (MSUs 19-22)

This is the primary, convenience-focused part of the FAW Cab Tilt Control Unit. This system allows the driver or technician to lift the cab by simply pressing the ‘Hydraulic cab tilt switch assy’ (3735080-A01) inside the cab.

1. ‘Electric pump assy’ (5002075B91W-C00): This is the “brain and muscle” of the electric system. This MSU is an integrated unit that combines the hydraulic pump and the electric motor into one assembly.

2. ‘Electric pump motor’ (5002180AA01-C00): This is the high-torque, 24V DC motor that drives the pump. Its “logic” is to provide high power for a short, intermittent duration. It draws a massive amount of current, which is why it cannot be wired directly to the dashboard switch.

3. ‘Electric pump relay assy’ (5002190B91W-C00): This is the “logic” that makes the system safe. The in-cab switch (3735080-A01) sends a small, low-amperage signal to this relay. This relay (a heavy-duty solenoid) then closes, handling the massive, high-amperage current needed by the motor. This protects the cab’s wiring from melting. This relay is a critical MSU.

4. ‘Electric pump shield assy’ (5002185B91W-C00): This is the system’s “armor.” This MSU protects the entire electric pump assembly from road debris, water spray, and ice. A missing shield is a common cause of premature motor corrosion and failure.

Core 2: The “Manual Logic” Backup System (MSUs 1-4)

This is the “redundancy logic” built into the FAW Cab Tilt Control Unit. This system ensures that even with a dead battery, a failed motor, or a blown relay, the cab can still be lifted for service.

1. ‘Manual pump – cab lift’ (5002070B91W-C00): This is the core of the manual system. It is a hydraulic hand pump, similar to a bottle jack. The technician inserts the truck’s jack handle (from the tool kit) into this pump’s socket and manually pumps it to raise the cab.

2. ‘Manual switch bracket assy’ (5002120B91W): This bracket holds the manual pump. More importantly, it holds the “changeover switch” or “selector valve.” The “logic” is that a technician must *first* turn this valve (often with the same jack handle) to change the hydraulic circuit from “electric mode” to “manual mode.” This prevents the manual pump from trying to push fluid “backwards” through the electric pump.

3. ‘Gasket’ (5002133B91W): This MSU provides the critical seal between the manual pump and its mounting bracket, preventing hydraulic fluid leaks under high pressure.

Core 3: The “Dual-Logic” Hydraulic Network (MSUs 8-13)

This group of MSUs is the “plumbing” of the FAW Cab Tilt Control Unit. These high-pressure hydraulic hoses are the arteries that connect *both* pumps to the main tilt cylinder.

1. The 3-Way Logic: ‘Hose assy – connect pump to 3-way joint’ (5002085B91W-C00)

This is the “logic” that allows the dual-pump system to work. The “3-way joint” (or a T-junction) is the point where the fluid line from the electric pump and the fluid line from the manual pump *meet*. From this junction, a single line then proceeds to the main tilt cylinder. This hose is the MSU that makes this “combined” logic possible.

2. The “Push/Pull” Logic: (MSUs 11 & 12)

The system uses a dual-action cylinder, which requires two hoses:

• ‘Hose assy – hydraulic cylinder push oil port’ (5002080B91W-C00): This is the “lift” line. The pumps push high-pressure fluid through this hose to *extend* the cylinder and lift the cab.
• ‘Hose assy – hydraulic cylinder pull oil port’ (5002100B91W-C00): This is the “lower” line. To lower the cab, the changeover valve is opened, allowing the cab’s weight to push fluid *out* of the cylinder and back to the reservoir through this hose.

3. Protection & Routing (MSUs 13, 16, 17):

These are the critical, often-overlooked MSUs. A ‘Deflector plate’ (5002141B91W) and ‘Shield-hydraulic oil pipe’ (5002146B91W) protect these vital hoses from road debris, stone chips, and high heat from the exhaust. A ‘Rubber seal’ (3724032-50A) protects a hose as it passes through a chassis member. A failure of these protective MSUs leads to a chafed, burst hose, which is the #1 failure point for any hydraulic system.

Core 4: The “Anti-Vibration” Fastener Logic (MSUs 5, 6, 14, 15, 18)

The entire FAW Cab Tilt Control Unit is subject to massive vibration. The fastener system is not just hardware; it is an engineered “anti-vibration” logic to prevent the pumps from shaking themselves loose.

‘Combination bolt’ (CQ1461035, CQ1460825, CQ1460820): The parts list calls for a total of eight (8) of these. The “Combination” logic is the most important feature. These bolts have a *captive, pre-attached lock washer* (either a spring washer or serrated head). This lock washer provides constant tension, making it physically impossible for the bolt to back out from vibration.

‘Hexagon nut’ (CQ34008): These four nuts are used on the other side of the bolts (e.g., CQ1460820). They are high-tensile, prevailing-torque “Nyloc” nuts. Their nylon insert binds to the threads, providing a *second layer* of anti-vibration logic. This dual-system (lock washer + lock nut) is what ensures the FAW Cab Tilt Control Unit remains securely fastened for the life of the vehicle.

FAW Cab Tilt Control Unit Parts List

The following table provides the complete, detailed breakdown of all 23 component types identified in the FAW Cab Tilt Control Unit diagram for the FAW CA4251P66K24T1A3E5 tractor.

Technical Specifications and Assembly Context

The specifications for the FAW Cab Tilt Control Unit are defined by its critical, dual-logic function. It combines a primary electric system for convenience and a manual backup system for safety and service redundancy.