What wires are connected to terminals 1, 2, and 3 of the three-wire ignition switch?
3 Answers
They are connected to the live wire, neutral wire, and ground wire respectively. Generally speaking, the red wire is the live wire, the blue one is the neutral wire, and the yellow-green one is the ground wire. If you are unsure, you can use a voltmeter to measure or a test pen to determine. If it carries electricity, it is the live wire; if not, it is the neutral wire. Precautions for wiring: Turn off the power: Before wiring, always remember to turn off the power switch at home. Develop this good habit. Never work with live wires to prevent the risk of electric shock, as the consequences could be unimaginable. Wrap with insulating tape: No matter what method you use for wiring, after completing the connection, it is best to wrap another layer of insulating tape around the connected part. It serves as insulation and also has fireproof functions, ensuring the safety of the wiring. Afterwards, the wires are less likely to develop problems.
On the car ignition switch, terminal 1 is typically connected to the battery positive wire (BAT input), terminal 2 is usually connected to the ignition or ACC wire (ignition system control), and terminal 3 primarily connects to the starter wire (ST terminal), ensuring proper power supply at each key rotation position. From a practical perspective, color coding varies significantly across vehicle models. For instance, older vehicles often use red for input, blue for central control, and green for starter, while newer models commonly employ black-yellow wires to indicate power input. In actual repairs, incorrect terminal connections can cause short circuits, leading to blown fuses or component damage. I recommend disconnecting the battery negative terminal before working, using a multimeter to test wire voltages, ensuring the ACC position illuminates the dashboard, the ON position activates the ignition system, and the START position momentarily engages the starter motor. Regularly inspect wiring harness wear to prevent spark hazards - veteran mechanics note 90% of issues originate here. Simple routine maintenance checks can prevent major troubles.
When I first started, I was curious about the wiring of the ignition switch terminals 1-2-3 and found it quite simple: Terminal 1 is the constant power input from the battery positive, always live; Terminal 2 controls intermediate functions like ACC (accessory) or IGN (ignition); Terminal 3 is dedicated to the starter. In practice, wire colors aren't standardized—for example, Ford might use red for input and brown for output, while Toyota could have orange in and blue out. Incorrect wiring risks short circuits, so switch replacement requires caution. I recommend beginners first use a test light to verify: turn the key to ACC to check if devices power on, then quickly turn to START to engage the engine before returning to ON. For safety, always disconnect the battery terminal to prevent accidents. Common issues like starting difficulties often trace back here. When DIY-ing, choose a compatible switch model to avoid high-resistance problems affecting performance.
