Understanding the Components:
* Choke Housing: This is the physical part on the carburetor that restricts airflow when cold.
* Bimetallic Spring: This spring is inside the choke housing and responds to heat, opening the choke as the engine warms up.
* Choke Pull-off: An electric solenoid that helps the choke open faster when the engine starts.
* Wiring Harness: The wires connecting the choke pull-off to the ignition system.
Common Wiring Configurations:
The choke pull-off typically receives power from the ignition system, usually through a resistor. This provides a lower voltage to the solenoid, preventing it from overheating and burning out. The most common configurations are:
* 12V directly to the pull-off (rare in 70 Mustangs): This is less common and generally not recommended because it can damage the pull-off.
* 12V through an ignition-switched resistor: This is the most likely scenario for your 1970 Mustang. The resistor limits the current to protect the pull-off. The resistor might be inline or integrated into a connector.
* From an ignition-switched source with an additional thermal switch: Some systems add a thermal switch that cuts power to the pull-off once the engine reaches operating temperature.
Steps to Wire (General Guide):
1. Identify Your Components: Locate the choke pull-off solenoid on your carburetor and trace its wires.
2. Consult Your Wiring Diagram: This is the most crucial step! A factory wiring diagram specific to your 1970 Mustang (including the engine and carburetor type) will show you exactly how the choke is supposed to be wired. You can often find these online through Mustang forums or restoration parts suppliers. A Haynes or Chilton manual might also be helpful.
3. Locate the Resistor (if applicable): If your system uses a resistor, identify it. It's often a small cylindrical component somewhere near the carburetor or in the main engine harness.
4. Trace the Wires: Follow the wires from the choke pull-off to their source. Note which wire is positive (+) and which is negative (-).
5. Connect the Wires (carefully!): Using your wiring diagram as a guide, carefully connect the wires to the correct terminals on the choke pull-off and the ignition system. If unsure, double-check your work multiple times.
6. Test the System: Reconnect the battery and turn the ignition key to the "ON" position. The choke pull-off should energize (you might hear a click). Start the engine and observe if the choke opens as it should.
Troubleshooting:
* Choke Doesn't Engage: Check the wiring, fuse (if applicable), and the pull-off solenoid itself. It might be faulty.
* Choke Doesn't Release: Check the bimetallic spring in the choke housing. It might be stuck or faulty. Ensure the resistor is functioning correctly if applicable.
* Choke Opens Too Quickly or Slowly: This could be due to a faulty bimetallic spring, a bad pull-off, or incorrect wiring.
Important Note: This is a general guide. Attempting this without the correct wiring diagram and understanding of your specific carburetor could damage your vehicle's electrical system. If you are not comfortable working with automotive electrical systems, it's best to seek the help of a qualified mechanic. Using the wrong voltage on the pull-off can easily burn it out.
