Upgrading a left-hand-drive (LHD) Honda Prelude (BB chassis) with a JDM automatic climate control system enhances cabin comfort and introduces advanced climate management features. This retrofit involves replacing the manual cable-operated system with electronically controlled components, including various sensors and a stepper motor for air mixing.

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Required Components for JDM Automatic Climate Control#

Successfully integrating the JDM automatic climate control system requires a comprehensive set of components from a donor JDM vehicle. It is crucial to source all listed parts to ensure full functionality.

Core System Components#

• Automatic Climate Control Unit: The main control panel and logic module.
• Wiring Harness: Dedicated harness for the automatic climate control system, often distinct from the manual system's wiring.
• Air Mix Motor: A stepper motor that replaces the manual cable for controlling the temperature blend door.
• Vacuum Heater Valve and Solenoid: Replaces the standard heater valve to allow electronic control of coolant flow to the heater core.
• Blower Motor Power Transistor: Replaces the resistive blower motor speed control module, enabling variable fan speed control.
• Blower Full-Speed Relay: A dedicated relay for maximum blower output.

Sensor Package#

• Sunlight Sensor: Typically located on the dashboard, it measures solar load to adjust cooling intensity.
• Cabin Temperature Sensor with Aspirator: Measures interior air temperature and uses a small fan (aspirator) to draw air over the sensor for accurate readings.
• Heat Exchanger Temperature Sensor: Monitors the temperature of the heater core.
• A/C Evaporator Temperature Sensor: Prevents the evaporator from freezing by monitoring its temperature.
• Outside Air Temperature Sensor: Provides ambient temperature data to the climate control unit.

Important

Ensure all components are in good working order before beginning the retrofit. Used components should be thoroughly inspected and cleaned.

Preparation and Pre-Installation Steps#

Before installing the JDM climate control components, proper preparation is essential for a reliable and long-lasting conversion.

• Component Cleaning: Thoroughly clean all acquired components. Old foam and debris can accumulate, affecting performance and air quality. Replace any deteriorated foam seals with new, appropriate material (e.g., closed-cell foam).
• Lubrication: Lubricate all moving parts, such as air door pivots and linkages, with a suitable PTFE-based or dirt-repellent grease to ensure smooth operation.

Installation Procedure#

The retrofit process involves significant disassembly of the dashboard and HVAC system. Refer to the factory service manual (FSM) for detailed instructions on dashboard removal and component locations specific to your vehicle.

1. Dashboard and HVAC Unit Removal#

• Carefully remove the dashboard and access the existing manual HVAC unit. This is a critical and time-consuming step.
• Remove the original manual air mixer unit.

2. Air Mix Motor Installation#

• The JDM air mixer unit, designed for right-hand-drive (RHD) vehicles, may have a mirrored configuration compared to the LHD manual unit. Adaptation or modification of the air mixer housing may be necessary to correctly install the JDM air mix motor and ensure proper blend door operation.
• Mount the JDM air mix motor to the air mixer housing, ensuring it correctly actuates the temperature blend door.

3. Sensor Integration#

• Cabin Temperature Sensor: Install the cabin temperature sensor and its aspirator. This often requires creating an opening for the aspirator's intake hose and sealing it properly (e.g., with a suitable O-ring and gasket maker).
• Sunlight Sensor: Mount the sunlight sensor on the dashboard in the designated location, typically near the windshield.
• Evaporator and Heat Exchanger Sensors: Install these sensors into their respective locations within the HVAC unit. Confirm correct placement using the FSM.
• Outside Air Temperature Sensor: Mount this sensor in its factory location, usually behind the front bumper or grille, ensuring it is exposed to ambient air and protected from direct engine heat.

4. Blower Motor Control Upgrade#

• Locate the blower motor resistor pack, typically on the blower motor housing. Remove it.
• Install the JDM blower motor power transistor in its place. This transistor allows for more precise and variable control of the blower motor speed.
• Install the blower full-speed relay into the appropriate location in the wiring harness or fuse box, as specified by the FSM.

5. Engine Bay Components#

• Vacuum Heater Valve: Replace the existing heater valve in the engine bay with the JDM vacuum-operated valve and its control solenoid. This typically involves modifying coolant lines and vacuum routing.

6. Wiring and Electrical Connections#

• Integrate the JDM climate control wiring harness. This will involve connecting the new harness to the main vehicle harness, power sources, and all installed sensors and actuators.
• Confirm all wiring connections against the factory service manual for both the donor JDM vehicle and your LHD Prelude. Pinout differences are common and critical to address correctly.

Warning

Incorrect wiring can cause damage to the climate control unit, other vehicle electronics, or pose a fire hazard. Always consult the appropriate factory service manuals for precise wiring diagrams and pinouts.

Verification and Testing#

After all components are installed and wired, perform thorough testing before fully reassembling the dashboard.

• Initial Power-Up: Turn the ignition to the ON position and observe the climate control unit. Ensure it powers on and displays correctly.
• Functionality Check: Test all modes (AUTO, A/C, heat, fan speeds, vent selection, recirculation, defrost) to confirm proper operation.
• Temperature Control: Verify that the system can accurately control and maintain desired cabin temperatures.
• Sensor Readings: If possible, use a diagnostic tool to check for proper sensor readings from all installed temperature and sunlight sensors.
• Airflow: Confirm that all blend doors and vent actuators are functioning correctly, directing airflow as selected.

Tip

Address any issues or error codes immediately. Consult the FSM for diagnostic procedures related to the automatic climate control system.

Important Considerations#

• Factory Service Manual: The factory service manual for both your specific LHD Prelude model and the JDM donor vehicle is an indispensable resource for this advanced retrofit. It will provide critical wiring diagrams, component locations, and disassembly/assembly procedures.
• Professional Assistance: If you are not comfortable with extensive automotive electrical work and dashboard disassembly, consider seeking professional assistance.
• Time Commitment: This retrofit is an advanced project requiring significant time and patience, often taking multiple days to complete.