This Heater Fan Regulator (part number 644178) is a direct-fit electrical component for a range of older Citroën and Peugeot models. It controls the blower motor speeds of the heating and ventilation system, restoring regulated airflow and reliable climate control. Designed for professional workshops and experienced DIY mechanics, this unit is a practical replacement when low or missing fan speeds, intermittent blower operation, or visible damage to the resistor pack is diagnosed. Supplied for a wide variety of models, it increases serviceability of older Stellantis vehicles and helps return comfortable cabin ventilation quickly.

Technical Information

• Manufacturer: Stellantis / Citroën / Peugeot
• Model: Citroën AX, Saxo, Xantia, XM, Berlingo, Xsara, ZX; Peugeot 106, 405, 406, 605, Partner
• Product Codes: 644178
• Other Numbers: Not Available

Function And Symptoms

The regulator (blower resistor) modulates current to the heater blower motor to provide selectable fan speeds. Typical symptoms of a failing unit include loss of one or more blower speeds (often only high speed remains), intermittent blower operation, humming or burning odor from the dash, or visible heat damage/corrosion on the resistor module. Replacing the regulator usually restores all fan speeds when the blower motor itself is serviceable.

How It Is Replaced

Typical replacement steps (vehicle-specific details may vary):

• Disconnect the negative battery terminal to prevent short circuits when working on electrical connectors.
• Access The Regulator: It is commonly mounted in the heater box near the blower motor. On many models this is reachable from the passenger footwell after removing the glovebox or an access panel.
• Unplug The Electrical Connector and remove the mounting screws securing the resistor pack to the heater housing.
• Replace The Unit And Reassemble: Fit the new regulator, secure screws, reconnect the plug and battery, then test all blower speeds and functions.
• Verify Operation: Test fan speeds at each setting and check for unusual noises or overheating. If only high speed works after replacement, inspect the blower motor for excessive current draw or worn brushes.

Installation Recommendations

• Use Basic Electrical Safety: Disconnect the battery before starting work and avoid pulling on wiring — release connector clips carefully.
• Inspect The Blower Motor And Connectors: A failing blower motor can overload and rapidly damage a new resistor; measure motor current if possible.
• Clean Contact Surfaces: Remove corrosion from connector pins and apply a small amount of dielectric grease to protect against moisture.
• Check Mounting Seals: Ensure the heater box seals are intact to prevent water ingress that can corrode the resistor in the future.

Why This Part Fails Most Often

• Overheating: Resistor tracks can burn out with age or when the blower motor draws excessive current.
• Corrosion And Moisture Ingress: Water or high humidity in the heater box causes connector and resistor failure.
• Electrical Problems: Loose connectors, shorts, or poor grounding increase heat and accelerate wear.
• Blower Motor Wear: Worn brushes or a partially seized motor increase current draw and shorten the resistor’s lifespan.

Additional Diagnostic Tips

Before replacing the regulator, check for:

• Voltage At The Connector With The Fan Switched On (compare to battery voltage).
• Excessive Current Draw From The Blower Motor—an indicator the motor may be failing.
• Visible Damage Or Burn Marks On The Old Resistor Pack.
• Intermittent Operation Caused By Loose Connectors—clean and reseat before replacement.

This replacement part is aimed at professional mechanics and competent DIYers familiar with electrical diagnostics and safe workshop practices. Proper inspection of the blower motor and connectors will maximize the lifespan of the new regulator and avoid repeated failures.

This direct-fit heater and air conditioning blower is designed for Peugeot 406 and Peugeot 607 vehicles and is referenced under manufacturer codes 659963H and 6441K9. A reliable replacement blower motor restores proper cabin airflow, improves heating and cooling performance, and eliminates noisy or intermittent fan operation. Suitable for professional workshops and skilled DIY fitters, the unit is a commonly searched spare part by its product numbers and is ideal when the original fan shows signs of wear.

Key Features

High-quality electric blower motor for climate control systems. Smooth and quiet operation, simple bolt-in replacement for common Peugeot installations, and compatibility with the vehicle’s ventilation housings. Restores full airflow through the heater core and AC evaporator, ensuring efficient defrosting and cabin temperature control.

How It Works

The blower motor forces air through the HVAC system’s heater core or air conditioning evaporator and into the passenger compartment. The motor’s rotor and bearings provide the rotational force while an electrical connector supplies power and speed control signals (via the blower resistor or control module). When the motor fails, airflow is reduced or stops and the climate system cannot regulate cabin temperature effectively.

Technical Information

• Manufacturer: Stellantis (Citroën / Peugeot)
• Model: Peugeot 406, Peugeot 607
• Product Codes: 659963H, 6441K9, NFP
• Other Numbers: 6441K9 | 659963H

Installation Recommendation

Always disconnect the vehicle battery before starting work. On most Peugeot 406 and 607 models the blower motor is located under the passenger-side dashboard, accessed after removing the glovebox or lower dash panels. Typical replacement steps:

1. Disconnect the negative battery terminal.
2. Remove the glovebox or lower dash trim to access the blower housing.
3. Disconnect the electrical connector and any associated wiring harness clips.
4. Remove mounting screws or clips securing the blower motor and extract the unit from the housing.
5. Install the new blower motor, secure fasteners to the correct torque, reconnect the electrical connector and reassemble trims.
6. Reconnect the battery and verify fan operation across all speed settings before completing reassembly.

Use proper hand tools and avoid forcing connectors. Replace any damaged seals or foam gaskets to prevent air leaks and reduce vibration. If the blower still does not function across all speeds after replacement, inspect the blower resistor or HVAC control module.

Why The Part Most Commonly Fails

• Brush Wear And Commutator Degradation — Over time the motor brushes wear down, leading to intermittent operation or complete failure.
• Bearing Wear — Bearings can seize or become noisy, increasing motor load and reducing lifespan.
• Debris And Leaves — Foreign objects entering the blower housing can jam the fan wheel or damage blades.
• Water Ingress Or Corrosion — Moisture from leaks or condensation can corrode terminals and internal components.
• Associated Component Faults — A faulty blower resistor or control module can mimic motor failure; verify electrical supply and control signals when diagnosing.

Notes For Mechanics And DIY Fitters

This blower is often searched by its product numbers (659963H, 6441K9), so include these codes when ordering. Inspect the HVAC housing and resistor assembly during replacement to prevent repeat visits. For high-mileage vehicles, consider checking cabin filter condition and clearing any debris from the intake to prolong the life of the new blower.