Key points
- Connect the red test lead to the positive terminal of the ignition coil and the black test lead to the negative terminal.
- Connect the red test lead to the positive terminal of the ignition coil and the black test lead to a good ground point on the engine block or chassis.
The ignition coil is a crucial component in your car’s engine, responsible for generating the high voltage needed to ignite the spark plugs. When your ignition coil malfunctions, you might experience various symptoms like engine misfires, difficulty starting, or a complete engine stall. Knowing how to check your ignition coil with a multimeter can save you time and money by allowing you to diagnose the problem yourself. This blog post will guide you through the process step-by-step, empowering you to tackle this common automotive issue.
Understanding the Ignition Coil
Before diving into the testing process, let’s understand the basics of the ignition coil. It’s essentially a transformer that increases the low voltage from your car’s battery to a high voltage needed to create a spark at the spark plug. The ignition coil has two primary windings: a primary winding and a secondary winding.
- Primary winding: This winding is connected to the battery and receives low voltage.
- Secondary winding: This winding is connected to the spark plug and produces high voltage.
When the ignition system activates, the primary winding is energized, creating a magnetic field. This magnetic field collapses when the circuit is broken, inducing a high voltage in the secondary winding, which travels to the spark plug, igniting the fuel-air mixture.
Gathering Your Tools
To check your ignition coil with a multimeter, you’ll need the following tools:
- Multimeter: A digital multimeter is recommended for accurate readings.
- Test leads: These are the probes that connect the multimeter to the ignition coil terminals.
- Safety glasses: Always wear safety glasses when working with electrical components.
- Gloves: Protect your hands from potential electrical shocks.
- Vehicle service manual: This manual will provide specific information about your vehicle’s ignition system and coil location.
Locating the Ignition Coil
The ignition coil is typically located near the engine, often mounted on the valve cover or near the spark plugs. Consult your vehicle’s service manual to pinpoint the exact location.
Checking the Ignition Coil for Continuity
The first step in testing your ignition coil is checking for continuity, which means ensuring that there’s a complete electrical path through the windings. This test helps identify any breaks or open circuits in the coil.
1. Disconnect the ignition coil: Locate the ignition coil and disconnect the wiring harness connected to it.
2. Set the multimeter to the ohms setting: Select the ohms setting on your multimeter, usually denoted by an Ω symbol.
3. Connect the test leads: Connect the red test lead to the positive terminal of the ignition coil and the black test lead to the negative terminal.
4. Check the reading: Observe the reading on the multimeter. A low resistance reading, typically between 0.5 and 5 ohms, indicates good continuity in the primary winding.
5. Repeat for the secondary winding: Disconnect the test leads and reconnect them to the secondary winding terminals. The resistance reading for the secondary winding should be significantly higher, typically between 5,000 and 20,000 ohms.
Checking the Ignition Coil for Resistance
The next step is to check the resistance of the ignition coil. This test helps determine if the coil is capable of generating the required high voltage.
1. Set the multimeter to the ohms setting: Ensure your multimeter is set to the ohms setting.
2. Connect the test leads: Connect the red test lead to the positive terminal of the ignition coil and the black test lead to the negative terminal.
3. Check the reading: Observe the reading on the multimeter. A low resistance reading, typically between 0.5 and 5 ohms, indicates a healthy coil. A high resistance reading or an open circuit indicates a faulty coil.
Checking for Ground Faults
A ground fault occurs when there is an unintended electrical path to ground. This can prevent the ignition coil from functioning properly.
1. Disconnect the ignition coil: Disconnect the wiring harness from the ignition coil.
2. Set the multimeter to the ohms setting: Ensure your multimeter is set to the ohms setting.
3. Connect the test leads: Connect the red test lead to the positive terminal of the ignition coil and the black test lead to a good ground point on the engine block or chassis.
4. Check the reading: The multimeter should display an open circuit, meaning there is no continuity between the coil terminal and ground. If the multimeter shows a low resistance reading, it indicates a ground fault.
Checking for Spark
If the continuity and resistance tests are satisfactory, you can check for spark directly at the spark plug. This test confirms if the ignition coil is producing a spark.
1. Disconnect the spark plug wire: Disconnect the spark plug wire from the spark plug.
2. Hold the spark plug wire near a grounded metal surface: Hold the end of the spark plug wire about 1/4 inch away from a grounded metal surface, like the engine block.
3. Have someone crank the engine: Ask someone to crank the engine while you observe the spark plug wire.
4. Check for spark: You should see a bright blue spark jumping from the spark plug wire to the grounded metal surface. If there’s no spark, the ignition coil might be faulty.
Replacing a Faulty Ignition Coil
If your tests indicate a faulty ignition coil, it’s time to replace it. This process typically involves the following steps:
1. Disconnect the battery: Disconnect the negative terminal of the battery to prevent electrical shocks.
2. Remove the old ignition coil: Disconnect the wiring harness and remove the old ignition coil from its mounting bracket.
3. Install the new ignition coil: Install the new ignition coil in the same position as the old one, ensuring it’s securely fastened.
4. Reconnect the wiring harness: Connect the wiring harness to the new ignition coil.
5. Reconnect the battery: Reconnect the negative terminal of the battery.
6. Start the engine: Start the engine and check for any issues.
Final Thoughts: A Spark of Success
By following these steps, you can effectively check your ignition coil with a multimeter and diagnose the problem yourself. Remember to always prioritize safety by disconnecting the battery and wearing appropriate safety gear. If you’re unsure about any step or encounter difficulties, consult a qualified mechanic for professional assistance.
Frequently Asked Questions
Q: What are the common symptoms of a faulty ignition coil?
A: Common symptoms include engine misfires, difficulty starting, engine stalling, reduced fuel efficiency, and a rough idle.
Q: How often should I check my ignition coil?
A: It’s generally recommended to check your ignition coil every 30,000 miles or as part of your regular vehicle maintenance schedule.
Q: Can I use a test light instead of a multimeter to check the ignition coil?
A: While you can use a test light to check for continuity, a multimeter provides more accurate readings and can help diagnose a wider range of issues.
Q: What are the factors that can cause an ignition coil to fail?
A: Factors that can lead to ignition coil failure include age, heat, moisture, electrical surges, and excessive vibration.
Q: Is it safe to drive with a faulty ignition coil?
A: While you might be able to drive with a faulty ignition coil for a short period, it’s not advisable. A faulty coil can lead to further damage to your engine and other components. It’s best to address the issue promptly.