The starting system of a vehicle is not just pressing a button or turning a key. The system required an electromagnet to start its motor. A starter solenoid is present in every car, serving as an electromagnet to initiate the engine’s start. The combustion engine has a starter solenoid as its essential factor. Primarily, these solenoids serve two functions: they act as a contactor and then connect to the starter engine’s battery. A starter solenoid is required for starting the engine; it acts as a switch or starting button of the engine. In this article, you will find information about the starter solenoid, its operation, signs of a fault, and methods for testing the starter solenoid.
What is a Starter Solenoid?
The starter solenoid is the combination of switches and solenoids. The electromagnetic device, which consists of coiled copper wire, connects the starter to the internal combustion engine. A solenoid is a bridge that makes the current flow from the ignition switch to control the flow of current to the starter motor. It is usually attached to the starter motor or sometimes mounted near it.
The magnetic field produced by the electric current is used to transform magnetic energy into mechanical energy. These solenoids often act as a valve to push or pull the magnetic component in a device. A solenoid has different elements.
| Components | Functions |
| Coil | A tightly wound helix |
| Armature | Movable core |
| Housing | Casing around the coil |
| Spring | Return the plunger to its original state. |
| Orifice | Opening |
| Ports | Fluid inlet and outlet |
Different kinds of solenoids are used in many operations:
| Solenoid | Features |
| AC-laminated solenoid | It is made of a wire coil and a metal core; it maintains the stray current and is used in medical devices and vehicles. |
| DC C-frame solenoid | It has a C-shaped frame wrapped around a coil, used in coin counters and scanners. |
| DC D-frame solenoid | It is compatible with AC devices. |
| Linear solenoid | Most commonly used solenoid, wrapped coil on a metal core. |
| Rotary solenoid | A grooved disc with a metal core is used in operation. |
| Proportional solenoid | It acts as a permanent magnet as well as a spring that returns the force. |
| Latching solenoid: | It is a linear actuator that helps in the excitation current that an application applies. |
How does a starter solenoid work?
There are different components in a solenoid that work in combination to carry out the operation. As it acts as an electromagnet, which means the current is supplied to the solenoid, which creates a magnetic field. This magnetic field will help to attract or repel the magnetic material in its housing. Another component that is a plunger will help in powering he intended component while providing the mechanical force. There are three basic steps in the operation of a starter solenoid:
- Sucking
- Holding
- Return
Sucking (Engagement Phase)
- The initial step occurs when the “start” button is pushed, which provides current to the pull-in coil and the hold-in coil.
- After that, the current flows to the armature, which causes it to spin slowly.
- This magnetic field will pull the plunger inward.
- The starter’s drive pinion will push the meshes with the engine flywheel.
- At the end of this phase, the contact plate inside the solenoid closes, providing full battery current to the starter motor.
Holding (Cranking Phase)
- In this phase of the starter solenoid, the Pull-in coil is of no use, as it is no longer receiving current.
- The coil that was spinning slowly will start spinning at full speed once the battery power reaches the armature.
- The engine starts its combustion process.
- The hold-in coil exerts a force on the plunger, causing it to remain in position. That force will cause the gear to lock in the flywheel.
Return (Disengagement Phase)
Once the engine starts, the key gets back to the start position:
- The pull-in and hold-in coils cancel the forces, and the circuit configuration changes.
- The return spring in the starter solenoid returns to its original position.
- This results in pulling the pinion gear from the flywheel, and the motor will disengage.
- The power from the motor is cut off, and the starter system shuts down.
How does a solenoid work with a starter motor?
The solenoid works in collaboration with the starter motor. As the ignition switch is turned to the start position, a small electrical current at 12 volts is discharged from the battery and through the solenoid. This small current energizes the solenoid, which then closes heavy-duty contacts to provide a much larger current to the starter motor. The starter receives this high current flow, and it turns over the engine.
The solenoid and starter motor act together and act as
- Electrical Bridge: The solenoid connects the battery to the starter motor circuit.
- Mechanical Link: It pushes the gear into the flywheel, allowing the motor to turn the engine over.
- Return Mechanism: Ensures the gear retracts once the engine is running.
The starter motor itself is most often of a specific type: either series-wound compound or permanent magnet, with the solenoid and its switch mounted directly on the motor. The solenoid is turned on not only to drive the motor but also to drive a plunger or lever that pushes the pinion gear of the starter into synchronization with the ring gear of the flywheel. The pinion gear features a built-in one-way clutch, ensuring that when the engine is running, the starter motor is not rotated at damaging speeds.
Signs of a faulty starter solenoid
A faulty solenoid can affect the whole process involved in starting an engine; there are sure signs associated with the defective starter solenoid:
- The sound from the solenoid should be a clicking noise in case of a fault. The holding coil in the solenoid keeps holding or contacts sealing off.
- Once you switch on the start solenoid, it won’t spin at full speed. This is due to a faulty connection between the solenoid and starter.
- The starter continues to rotate even when the starter button has disengaged. In this case, there must be a burnout in the solenoid contact.
- Last but not least is the sign that the drive gear cannot get into return or reverse. And it continues to rotate once the start button is disengaged. The reason for the fault may be that the burned-out movable core and the return spring have lost their elasticity.
How do I test a starter solenoid?
Different methods can be used to test the starter solenoid to determine if it is functioning properly.
| Test | Procedure |
| Testing the solenoid with a screwdriver | The process is simple to assess the clicking sound produced in the starter solenoid. The screwdriver is used to connect the terminal ends. If the starter does not start, it means that the starter is not working; if it starts, it means the solenoid is not working. |
| Digital Multimeter Testing | For using this test, the car ignition must be off.
Connect the M and B terminals of the solenoid to the multimeter. If the screen displays zero ohms in the continuity test, then it is necessary to replace the solenoid. |
| Starter Solenoid Sucking Coil Test | You need to test the starter solenoid. For this, connect the battery’s positive terminal to the starter terminal 50 and the negative to terminal C. If the drive gear is not moving forward, then it means that the solenoid is working correctly. |
| Starter Solenoid Holding Coil Test | It is the same as the sucking coil test; replace the negative terminal and connect to the holding terminal. If the driver gears in reverse the direction this indicates the deformation. |
| Starter Solenoid Spring Test | Disengage the negative terminal of the battery if the driver gear does not reverse rapidly. It means that the solenoid needs to be replaced. |
Frequently Asked Questions
What is the difference between a starter solenoid and a starter relay?
The starter solenoid and starter relay are often mistaken for being the same, but they serve different purposes.
- Starter Solenoid: It is a high-current device typically located on or beside the starter motor, which also drives the gear that connects to the engine.
- Starter Relay: This is a low-current intermediate switch that transmits the signal coming out of the ignition switch to the solenoid.
Both components can be present in today’s cars, although the solenoid is the one that directly starts the engine.
Will a damaged solenoid drain the battery?
Yes, a damaged solenoid can drain the battery only under certain circumstances, such as internal contacts that are stuck closed, which will keep the motor engaged even after the engine starts.
What is the typical lifespan of a starter solenoid?
The typical lifespan of the starter solenoid is around 15 years, or approximately 60,000 to 100,000 miles in terms of mileage, before it needs to be replaced.
Can I bypass the solenoid to start my vehicle?
Yes, you can bypass the solenoid in case the starter motor doesn’t rotate properly or makes a continuous noise; the solenoid switch may be faulty. In an emergency, you can start the engine by connecting the battery’s positive terminal to the starter’s terminal B with a lead wire. Once the engine starts, disconnect the wire immediately and seek professional repair.