Starter solenoid works in the engine compartment near the car battery. It is used to send a high amperage current from the battery to the starter motor. When the engine is running and you press the brake pedal, the current which was going to the starter motor switches direction and runs through your brake lights, illuminating them. This is why a bad solenoid can cause your brake lights to not work, even though it can be tested with a multimeter. So, it’s important to know how to test a starter solenoid with multimeter.
What is a Starter Solenoid?
A starter solenoid is a small electrical switch that is operated by the car’s ignition system. It is used to send a high amperage current from your battery to your car’s starter motor, which turns the engine over until it starts. In short, without a starter solenoid or its equivalent installed, you cannot start your car! If you want to know how to measure amps with a digital multimeter then you can read my blog.
Here’s a breakdown of its two key functions:
- Electromagnetic Gateway: The solenoid functions like a relay. It receives a small current from the ignition switch when you turn the key. This activates an electromagnet within the solenoid, which in turn pulls a metal plunger. This action throws a heavy-duty switch, completing the circuit between the battery and the starter motor. With this connection established, a surge of current flows from the battery to the starter motor, cranking the engine.
- Engaging the Starter Pinion (in some models): In some car designs, the solenoid not only controls the electrical connection but also physically engages the starter motor’s pinion gear with the engine’s flywheel ring gear. This crucial action ensures the starter motor can effectively rotate the engine to initiate combustion.
How it Works: A Step-by-Step Breakdown
- Turning the Key: When you turn the ignition key, a small current is sent from the ignition switch to the solenoid’s control coil.
- Electromagnetic Activation: This current energizes the coil within the solenoid, transforming it into a temporary electromagnet.
- Plunger in Action: The energized coil attracts a metal plunger inside the solenoid.
- Heavy Duty Switch Engagement: The movement of the plunger throws a heavy-duty switch within the solenoid. This switch acts like a bridge, connecting the battery’s high current directly to the starter motor.
- Engine Cranking: With the powerful current flowing, the starter motor whirs to life, engaging the flywheel and cranking the engine.
- Disengaging (After Start): Once the engine starts, you release the key, and the current to the solenoid ceases. The electromagnet deactivates, and a spring within the solenoid pulls the plunger back, disconnecting the starter motor from the battery. This prevents the starter from continuously running and potentially damaging itself or the engine.
Best Multimeter for Starter Solenoid Testing
#1
4.7/5
Klein MM700 Multimeter
If you don’t choose a multimeter yet then Klein mm700 should be your priority. It can do all types pf testing required to test any solenoid.
Why a Starter Solenoid is Important for a Car’s Ignition System
In order for your car to start, there are six things needed:
- Battery Voltage
- Engine Cranking Speed
- Spark Plugs
- Compression
- Oxygen in Fuel mixture
- Firing of the spark plugs at the right time, and in the right order.
The starter solenoid must close while the engine is cranking, allowing it to get enough electrical power from the battery to create a spark in each cylinder of your car. A faulty solenoid will not allow this current through, which is why you will see your car’s engine cranking, but not starting.
What You’ll Need for testing starter solenoid?
- Digital multimeter (Fluke 117 Electrician Multimeter)
- Some wire connectors (such as for automotive use)
- An automotive wire connector stripped of its rubber, usually, just two wires inside the connector, not four like an electrical component would typically have.
- Something to disconnect the battery cable from the battery’s positive and negative terminal (wire cutters or something else).
If you don’t know about multimeters then I have made a detailed list of the best multimeters for automotive use. You can also buy these items from local auto parts store.
Step by step guide on How to Test a Starter Solenoid with Multimeter
How to test a starter solenoid with multimeter, step by step guide:
- Turn off your car engine and open the hood of your car
- Locate the starter solenoid in between the battery and the starter motor (see picture)
- Use your multimeter to read voltage directly across the battery terminals. It should be 12 volts when the key is turned to “ON” or “ACC.”
- Now touch one of your meter’s probes to each end of the solenoid- one on each end of the solenoid.
- There should be DC voltage when you read across the solenoid and it should be 12 volts. If your reading shows 0 volts, then you have an open circuit, which means that your solenoid is bad and needs to be replaced or there’s a break somewhere else between your battery and starter motor (test with a jumper wire to see if the problem is the starter solenoid or elsewhere). If you get 12 volts, then your reading is showing that there’s continuity in your circuit.
- Replace your starter solenoid if it has either an open circuit or no continuity. Otherwise, continue troubleshooting by checking for the voltage drop across ground terminal at different points in your engine, including the positive terminal. This test will require you to remove some of the fuses in your car’s fuse box or even disassemble some parts of your car for better access.
I have made a separate guide of car battery testing and best battery tester for you. Visit for more details.
Starter Solenoids and the Failures That They Cause
There are several common problems with starter solenoids:
- Open circuit (bad connection somewhere in your car’s wiring)
- Short circuit (a short caused by bad or corroded wiring, which is essentially an “open” that allows electricity to pass through it too easily and thus cannot provide the crank of power necessary to start your car).
- Voltage drop (a bad solenoid, which is caused by the solenoid not being able to send high amperage current through its wires)
- No continuity (the wire has either come loose or there’s a break somewhere in the wire- this will require you to perform further testing to determine where the problem lies- which is why it can be difficult to test a starter solenoid with a multimeter).
- Component Interference (a bad solenoid might not be able to open and close when needed because of interference from other components, such as a faulty ignition switch or smaller cylinder attached to it).
- There might be an option that your car battery is dead.
Conclusion
Replacing your starter solenoid is a quick, simple and relatively inexpensive task that can be done by just about anyone. Testing a starter solenoid with a multimeter is a quick way to see whether you have continuity from the battery terminal to the ignition key. If there’s no continuity, then you need to do further testing to find the culprit. This may require disassembling certain parts of your car or even removing some of your car’s fuses– if you’re not sure what you’re doing, it might be best to take your car in for professional testing and repair so as to avoid further damage to your vehicle.
If you would like more information about how to test car relays then I have made a separate guide for you. Hope you now you know, how to test a starter solenoid with multimeter.
FAQs
What is the impact of battery terminals on starter solenoids?
Battery terminals are directly connected to the starter solenoid of all vehicles. If there is any corrosion or losing then it may be possible that they start missing. To cope with this issue always try to grease your car battery terminals periodically. If your car battery negative terminal is exposed or not insulated then there is no big deal but always insulate your positive terminal from body because it can cause fire in your car electrical system or damage associated items.
What happens if your battery voltage drop?
If your car battery is dying, or if it is dropping voltages, you will not be able to start the battery from the ignition. This is because the starter solenoid will not be receiving any current. The only thing you can do is jump start your car. However, never use a thin wire to jumpstart your car, it will not handle high currents.
How to bypass the ignition switch of a car?
The ignition switch on cars is a mechanical piece. This part of the car is not electrical and can be bypassed by removing a few bolts with a wrench. It’s a simple fix that most people could do if they had the right tools.
Moreover, it is a common misconception that the ignition switch is the only thing needed to start a car. In reality, there are many ways to bypass the ignition switch. One way to do it is by using a screwdriver and turning the steering wheel back and forth. Another way is by positioning your hand under where you can reach up from behind and push down on the key, which will unlock it from the lock.
