When it comes to the electrical system of a vehicle, the starter relay plays a crucial role in starting the engine. It acts as a switch between the battery and the starter motor, ensuring that the motor receives enough power to crank the engine. In this article, we will be discussing the 12-volt starter relay wiring diagrams in detail, explaining how to wire the relay, what each wire does, and answering common questions related to starter relays.
What is a 12 Volt Starter Relay?
A starter relay is an electrical switch that is used to control the flow of high current between the battery and the starter motor. It is designed to handle the high current required by the starter motor, which typically exceeds 100 amps. The relay acts as a safety device that prevents the starter motor from engaging if there is a fault in the system.
A 12-volt starter relay is a type of starter relay that is designed to operate on a 12-volt electrical system. Most modern cars, trucks, and motorcycles use a 12-volt system, where the battery produces 12 volts of electricity. This makes the 12-volt starter relay a common component in most vehicles.
Wiring a 12 Volt Starter Relay
The wiring of a 12-volt starter relay is relatively simple. The relay has four terminals: two control terminals and two power terminals. The two control terminals are usually labeled as “S” and “I”, while the two power terminals are usually labeled as “B” and “M”.
The “S” terminal is used to connect the relay to the ignition switch. This wire supplies power to the relay when the key is turned to the “start” position. The “I” terminal is used to connect the relay to the positive terminal of the coil. This wire supplies power to the coil when the relay is activated.
The “B” terminal is used to connect the relay to the battery. This wire supplies power to the relay at all times. The “M” terminal is used to connect the relay to the starter motor. This wire supplies power to the starter motor when the relay is activated.
The wiring diagram for a 12-volt starter relay is shown below:
| Terminal | Wire Color | Description |
|---|---|---|
| S | Red | Ignition Switch |
| I | Yellow | Coil Positive |
| B | Black | Battery |
| M | Green | Starter Motor |
How to Wire a 12 Volt Starter Relay
Wiring a 12-volt starter relay is a simple process that can be done by anyone with basic electrical knowledge. Here is a step-by-step guide on how to wire a 12-volt starter relay:
Step 1: Disconnect the negative (-) cable from the battery.
Step 2: Locate the starter motor and the starter relay. The starter relay is usually located near the battery or the starter motor.
Step 3: Identify the four terminals on the starter relay. The terminals should be labeled as “S”, “I”, “B”, and “M”.
Step 4: Connect the “B” terminal of the relay to the positive (+) cable on the battery.
Step 5: Connect the “S” terminal of the relay to the ignition switch using a red wire.
Step 6: Connect the “I” terminal of the relay to the positive (+) terminal of the coil using a yellow wire.
Step 7: Connect the “M” terminal of the relay to the starter motor using a green wire.
Step 8: Reconnect the negative (-) cable to the battery.
FAQ
What happens if the starter relay fails?
If the starter relay fails, the starter motor will not receive power, and the engine will not start. In some cases, the starter motor may produce a clicking sound when the key is turned, indicating a faulty starter relay.
Can a bad starter relay drain the battery?
Yes, a bad starter relay can drain the battery. If the relay is stuck in the “on” position, it can cause the starter motor to run continuously, draining the battery.
How do you test a starter relay?
You can test a starter relay using a multimeter. First, disconnect the wires from the relay. Then, set the multimeter to the continuity mode and touch the two probes to the relay terminals. If there is continuity between the “S” and “M” terminals, the relay is functional. If not, the relay may be faulty and needs to be replaced.
What is the lifespan of a starter relay?
The lifespan of a starter relay varies depending on the manufacturer and the quality of the product. On average, a starter relay can last between 50,000 to 100,000 miles. However, this can vary depending on the usage and maintenance of the vehicle.
Can you bypass a starter relay?
Yes, you can bypass a starter relay by connecting the positive (+) cable directly to the “M” terminal of the starter motor using a jumper wire. However, this is not recommended as it can be dangerous and can cause damage to the electrical system.
By following the above instructions, you can learn how to properly wire a 12-volt starter relay and understand common questions about starter relays. Make sure to always follow safety procedures when working with electrical systems, and consult a professional if you are unsure about any aspect of the process.
