Four Seasons 38644 Porous Orifice Tube: Installation and Maintenance Manual

1. Introduction

The Four Seasons 38644 Porous Orifice Tube is a critical component within an automotive air conditioning (AC) system. Its primary function is to regulate the flow of refrigerant into the evaporator, causing a pressure drop that allows the refrigerant to expand and cool. This process is essential for the AC system to effectively remove heat from the vehicle's cabin. Proper installation and maintenance are vital for optimal AC performance.

2. Product Description

The Four Seasons 38644 is a dark grey porous orifice tube designed for specific automotive AC applications. It is manufactured to meet industry standards for fit and function, ensuring reliable performance in compatible systems.

• Product Type: Auto Part
• Package Quantity: 1
• Dimensions: Approximately 4.88 x 2 x 1.38 inches
• Weight: Approximately 0.48 ounces

Image 2.1: The Four Seasons 38644 Dark Grey Porous Orifice Tube. This image displays the complete orifice tube, featuring its dark grey body, green O-rings, and the porous filter section.

Image 2.2: The Four Seasons 38644 Orifice Tube shown with a hand for scale, indicating a length of approximately 4.1 inches (10 cm). This image helps visualize the physical size of the component.

3. Setup and Installation

Installation of an orifice tube requires specialized knowledge and tools for handling automotive AC systems. It is strongly recommended that this procedure be performed by a certified automotive technician. Improper installation can lead to system damage, refrigerant leaks, and personal injury.

3.1. Safety Precautions

• Always wear appropriate personal protective equipment (PPE), including safety glasses and gloves.
• Refrigerant is under high pressure and can cause frostbite or other injuries.
• Ensure the AC system is fully discharged by a professional using proper recovery equipment before attempting any work.
• Never vent refrigerant into the atmosphere.

3.2. General Installation Steps (Professional Installation Recommended)

1. Locate the Orifice Tube: The orifice tube is typically located in the liquid line, often near the condenser or evaporator. Consult your vehicle's service manual for the exact location.
2. Discharge AC System: Ensure the AC system is completely discharged and evacuated by a professional.
3. Disconnect Line: Carefully disconnect the AC line where the orifice tube is housed. Be prepared for residual refrigerant or oil.
4. Remove Old Orifice Tube: Use a specialized orifice tube removal tool to extract the old tube. Note its orientation for correct installation of the new part.
5. Inspect and Clean: Inspect the AC lines for debris or contamination. Clean as necessary.
6. Install New Orifice Tube: Insert the new Four Seasons 38644 orifice tube, ensuring it is oriented correctly as per the vehicle manufacturer's specifications. The porous filter end typically faces the evaporator.
7. Reconnect Line: Reconnect the AC line, ensuring all connections are secure and new O-rings are used where specified.
8. Evacuate and Recharge: Evacuate the AC system to remove air and moisture, then recharge with the correct type and amount of refrigerant and PAG oil, as specified by the vehicle manufacturer.
9. Test System: Start the vehicle and test the AC system for proper operation and cooling. Check for any leaks using a leak detector.

4. Operating Principles

The Four Seasons 38644 Porous Orifice Tube operates as a fixed restriction device within the AC system. High-pressure liquid refrigerant flows through the small orifice, causing a significant drop in pressure and temperature. This low-pressure, low-temperature refrigerant then enters the evaporator, where it absorbs heat from the vehicle's interior, providing cooling. The porous filter section helps to prevent debris from entering and potentially damaging the evaporator or other sensitive components.

5. Maintenance

The orifice tube itself is a passive component and does not require routine maintenance. However, its proper function relies on the overall health of the AC system. Regular maintenance of the entire AC system can prolong the life of all components, including the orifice tube.

• System Checks: Periodically have your AC system inspected by a qualified technician for proper refrigerant levels, leaks, and overall performance.
• Refrigerant Quality: Ensure that only the correct type and clean refrigerant is used in your system. Contaminated refrigerant can lead to clogging of the orifice tube.
• Filter/Drier Replacement: The receiver/drier or accumulator/drier should be replaced whenever the AC system is opened for major repairs, as it helps filter contaminants and absorb moisture, protecting the orifice tube.

6. Troubleshooting

A clogged or faulty orifice tube can significantly impair AC system performance. If you experience any of the following symptoms, the orifice tube may need inspection or replacement:

• Poor Cooling: The AC system blows warm or only slightly cool air.
• Intermittent Cooling: The AC cools intermittently or only at certain engine speeds.
• High Head Pressure: Abnormally high pressure readings on the high-side of the AC system.
• Frost on Lines: Frost or ice forming on the liquid line before the evaporator.

If these symptoms occur, consult a professional automotive technician for diagnosis and repair. Attempting to diagnose or repair AC system issues without proper training and equipment can be dangerous.

7. Specifications

8. Warranty and Support

For specific warranty information regarding the Four Seasons 38644 Porous Orifice Tube, please refer to the documentation provided with your purchase or contact Four Seasons customer support directly. General support and technical assistance can be obtained through the official Four Seasons website or by contacting their authorized distributors.

Image 8.1: The official Four Seasons logo, representing the brand's commitment to quality automotive parts.