How To Wire Electric Choke

How to Wire an Electric Choke: A Comprehensive Guide for Car Enthusiasts

Are you tackling a carburetor rebuild or dealing with a malfunctioning choke system in your classic car or vintage truck? Understanding how to wire an electric choke is crucial for proper engine starting and smooth running, especially in colder temperatures. This comprehensive guide will walk you through the process, covering everything from understanding the components to troubleshooting common problems. We'll delve into the electrical workings, provide clear wiring diagrams, and offer practical tips for a successful installation or repair. Whether you're a seasoned mechanic or a DIY enthusiast, this guide will equip you with the knowledge and confidence to tackle this essential automotive task.

Understanding the Electric Choke System

Before jumping into the wiring, let's understand how an electric choke works. Unlike manual chokes that rely on a cable and lever, electric chokes utilize a small electric motor to control the choke plate. This plate restricts airflow into the carburetor, enriching the fuel mixture for easier cold-starting. The system is controlled by a thermal sensor, often built into the choke housing itself, and a control unit.

The basic components of an electric choke system include:

• The Choke Housing: This houses the choke plate and the thermal sensor. The choke plate is a butterfly valve that partially blocks the airflow.
• The Electric Motor: This small motor is responsible for moving the choke plate to the desired position.
• The Thermal Sensor (Bimetallic Strip): This sensor detects the engine temperature. As the engine warms up, the sensor's resistance changes, signaling the control unit to gradually open the choke.
• The Control Unit (sometimes integrated into the choke housing): This unit receives the signal from the thermal sensor and controls the electric motor to adjust the choke plate position accordingly.
• Wiring Harness: This connects all the components together. It typically includes wires for power, ground, and the signal from the thermal sensor.

Steps to Wire an Electric Choke

Wiring an electric choke can seem daunting, but with a methodical approach, it becomes manageable. Remember to always disconnect the battery's negative terminal before starting any electrical work.

1. Identify Your Components and Wiring Harness:

Begin by carefully inspecting your electric choke assembly. Identify the electric motor, thermal sensor, and any other components. Examine the wiring harness; you'll typically find three wires:

• Power Wire: This wire supplies power to the electric motor. This is often a thicker gauge wire.
• Ground Wire: This provides a ground connection for the circuit.
• Sensor Wire: This wire carries the signal from the thermal sensor to the control unit, regulating the choke's position.

2. Prepare the Installation Location:

Ensure you have a clear and accessible location to mount the choke housing on your carburetor. The choke housing needs to be securely fastened to prevent vibrations from damaging the internal components.

3. Connect the Power Wire:

The power wire should be connected to a switched 12V power source. This means the power should only be supplied when the ignition is switched on. A convenient location might be the ignition switch harness or a fused circuit dedicated to the carburetor's electrical components. Always use the correct gauge wire and appropriate connectors to prevent overheating or short circuits.

4. Connect the Ground Wire:

The ground wire needs to be securely connected to a clean, bare metal surface on the engine block or chassis. A poor ground connection can lead to erratic choke operation. Use a sturdy ground wire and ensure a tight connection.

5. Connect the Sensor Wire:

The sensor wire connects to the control unit (often integrated within the choke housing). This wire carries the temperature signal from the thermal sensor, which determines how much the choke needs to open. Make sure this connection is secure and clean.

6. Test the Installation:

Once all the connections are made, carefully reconnect the battery. Turn the ignition key to the "ON" position (without starting the engine). The choke should move to the fully closed position. As the thermal sensor warms up (you can use a heat gun carefully for testing purposes), the choke plate should gradually open.

7. Final Checks and Engine Start-Up:

After the wiring is completed and tested, start the engine. Observe the choke operation. It should start in a fully closed position and gradually open as the engine warms up. If the choke doesn't operate correctly, review the connections and troubleshoot any potential problems.

Detailed Wiring Diagrams and Variations

While the basic principles remain consistent, the specific wiring diagrams might vary slightly depending on the make, model, and year of your vehicle and the type of electric choke you are using. Some electric choke units have a single wire for both power and sensor signal, while others have separate wires for power and a sensor signal. Always refer to your specific carburetor's instructions and wiring diagrams for accurate guidance. Below are examples of simplified diagrams, but always prioritize the manufacturer's specifications:

Simplified Diagram (Three-Wire System):

+12V (Switched)  ----->  Power Wire  ----->  Electric Choke Motor  -----> Ground
                                                                     |
                                                                     |
                                                                     V
                                                    Thermal Sensor -----> Sensor Wire -----> Control Unit (often in Choke Housing)

Simplified Diagram (Two-Wire System, with combined power/sensor):

+12V (Switched)  ----->  Combined Power/Sensor Wire  ----->  Electric Choke Motor  -----> Ground

                                                                     |
                                                                     V
                                                                  Thermal Sensor (Integrated in Control Unit)

Important Note: These diagrams are simplified representations. Your actual wiring might involve additional components like fuses or relays for safety and protection.

Troubleshooting Common Electric Choke Problems

If your electric choke is not working correctly, here's a systematic troubleshooting approach:

• Check the Power Supply: Ensure the 12V power is reaching the choke motor when the ignition is on. Use a multimeter to verify voltage.
• Check the Ground Connection: A poor ground connection is a frequent cause of problems. Clean the ground point and ensure a secure connection.
• Inspect the Wiring Harness: Check for any broken, frayed, or corroded wires. Repair or replace as necessary.
• Test the Thermal Sensor: Using a multimeter, check the resistance of the thermal sensor at various temperatures. If it's not changing resistance as expected, the sensor may be faulty.
• Test the Choke Motor: With power applied, check if the motor is functioning. If it's not turning, the motor might be defective.
• Inspect the Choke Plate Mechanism: Ensure the choke plate moves freely and isn't binding. Clean and lubricate if needed.
• Check the Control Unit (if separate): If the choke has a separate control unit, check its functionality and connections.

FAQs about Electric Chokes

Q: Can I convert a manual choke to an electric choke?

A: Yes, it's possible, but it requires careful planning and potentially modifying the carburetor. You'll need to choose a compatible electric choke unit and fabricate a mounting bracket if necessary. This is an advanced modification.

Q: Why is my electric choke sticking?

A: This could be due to several factors including a faulty motor, a binding choke plate, or accumulated dirt and debris. Clean and lubricate the moving parts and check the motor's operation.

Q: My choke stays closed even when the engine is warm. What could be wrong?

A: This suggests a problem with the thermal sensor, the control unit, or the wiring connecting them. Check the sensor's resistance and the wiring for continuity.

Q: Can I use a universal electric choke kit?

A: While universal kits exist, it's crucial to ensure compatibility with your specific carburetor. The choke's dimensions, linkage, and electrical specifications must match.

Q: How important is it to have a functioning electric choke?

A: A properly functioning electric choke is essential for easy cold starting and optimal fuel efficiency, especially in colder climates. A malfunctioning choke can lead to poor fuel economy and difficult starting.

Conclusion: Mastering the Art of Electric Choke Wiring

Wiring an electric choke might seem intimidating at first, but with a methodical approach, the right tools, and a clear understanding of the system, it becomes a manageable task. This guide has provided a comprehensive overview of the process, covering the components, wiring steps, troubleshooting, and frequently asked questions. Remember to always prioritize safety by disconnecting the battery's negative terminal before starting any electrical work and double-check all your connections. With patience and attention to detail, you'll be able to successfully wire your electric choke and enjoy the smooth and efficient operation of your classic car or truck engine. Remember to consult your vehicle's specific manual and the instructions that came with your choke for the most accurate guidance. Good luck!