FAW Fan: The 2 Critical Secrets to Flawless, Powerful Cab Airflow

Welcome to this in-depth engineering analysis of the FAW Fan assembly (Assembly 711). This is the “active core” of the entire HVAC system, the “logic” assembly that functions as the “lungs” for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This is the system responsible for generating and controlling the flow of all heated and cooled air within the cab.

The FAW Fan assembly is a “dual-logic” system. It is not just a fan; it is a “smart” blower module. It consists of two key components: the ‘Motor with impeller assy’ (8101045-A65-C00), which is the “muscle” that moves the air, and the ‘Speed control module’ (8101080-A65-C00), which is the “brain” that regulates the airflow.

This system works in direct concert with the ‘Automatic A/C’ assembly (Assembly 709). This in-depth guide is a critical resource for HVAC technicians and parts specialists. We will deconstruct the entire FAW Fan assembly into its two distinct serviceable components, analyzing the “centrifugal” logic of the impeller and the “variable-speed” (PWM) logic of the control module.

Component 1: The “Muscle” & “Centrifugal” Logic (8101045-A65-C00) (The “Longer” Module)

The ‘Motor with impeller assy’ (8101045-A65-C00) is the “heart” of the FAW Fan system. This is the primary serviceable unit, combining the 24V DC motor and the “squirrel cage” fan into a single, pre-balanced assembly. Its “logic” is to create high-pressure, high-volume airflow.

1. The “Impeller” Logic (Centrifugal Force):

The “impeller” (叶轮) is the “squirrel cage” or “centrifugal” fan wheel. Its “logic” is fundamentally different from a simple “blade” fan.

A blade fan (like a desk fan) is an “axial” fan; it pushes air in a straight line. This FAW Fan is a “centrifugal” fan. Its “logic” is to pull air in through its center (the “eye”) and then use centrifugal force to “fling” the air outwards at a 90-degree angle at high speed.

This “centrifugal logic” is essential for an HVAC system. It does not just create “flow” (CFM); it creates “static pressure.” This “pressure logic” is what gives the air the *force* it needs to push through the highly-restrictive, dense-fin cores of the ‘Evaporator’ (Assembly 709) and ‘Heater Core’ (Assembly 709), and then through the ‘Blower Ducts’ (Assembly 710) to the driver’s feet.

2. The “Motor” Logic (24V DC):

This is the “muscle” of the FAW Fan. It is a high-torque, 24-volt DC motor designed for long life in a high-heat environment. Its “logic” is simple: to provide the high-speed (3000+ RPM) rotation needed to make the impeller effective.

Failure Logic (Motor): This is a primary failure point.

• Squealing: The motor’s internal bearings (bushings) wear out from heat and dust, creating a loud, high-pitched “squeal” or “chirp” when the fan is on.
• “Dead” Fan: The motor’s “brushes” (the carbon contacts that deliver power) wear down to nothing, and the motor stops working completely.

3. The “Balanced Assembly” Logic:

This component is a “welded assembly” (总成) for a critical “NVH” (Noise, Vibration, Harshness) logic. The plastic impeller is “spin-balanced” on the motor shaft at the factory, often with small, strategically-placed metal clips.

This “balance logic” is essential. A 1-gram imbalance at 3,000 RPM creates a *massive* “wobble” and a low-frequency “drone” that can be felt through the entire dashboard. This is why you *cannot* replace just the motor or just the fan wheel. The entire ‘Motor with impeller assy’ must be replaced as a single, pre-balanced serviceable unit to ensure a silent, vibration-free operation of the FAW Fan.

Core 2: The “Variable Speed” Logic (Component 2)

The ‘Speed control module’ (8101080-A65-C00) is the “brain” of the FAW Fan. This is the component that tells the “muscle” (Component 1) how fast to spin. This is a critical serviceable unit for the “Automatic” A/C.

“Resistor” Logic (Manual): In a simple, “manual” A/C system, this component is a “blower motor resistor.” It’s a set of coiled-wire resistors. “Low” speed forces power through 3 resistors. “Medium” forces it through 1. “High” bypasses all resistors.

“Module” Logic (Automatic): This part is a “Module” (模块). This “logic” is far more advanced. It is a solid-state “final stage resistor” containing transistors. Its “logic” is to receive a “Pulse Width Modulation” (PWM) signal from the ‘Automatic A/C operating mechanism’ (Assembly 710, Component 19).

This “PWM logic” allows the A/C “brain” to request *any* fan speed. It can ask for 20% speed, 47% speed, or 81% speed. This “infinitely variable” speed is the “logic” that allows the automatic climate control to *silently* and *precisely* maintain the cab’s temperature.

Failure “Logic”: This component is the #1 cause of FAW Fan speed problems. Its transistors get extremely hot (it’s mounted in the air duct to be cooled by its own airflow). When they overheat and fail, the “logic” breaks.

The classic symptom: “The fan only works on HIGH.” This happens because the “High” setting is a “failsafe logic” that *bypasses* this module completely and sends 24V directly to the motor. If the fan works on high but *not* on any other speed, this ‘Speed control module’ is the failed serviceable part.

FAW Fan Parts List & Specifications

The following table provides the complete, detailed breakdown of all 2 component types identified in the FAW Fan assembly for the FAW CA4251P66K24T1A3E5 tractor.

Specifications

The specifications for the FAW Fan are defined by its function as the “brain and muscle” of the cab’s HVAC airflow system.