How To Test Ignition Switch (Expert Guide)

The ignition switch, as its name implies, governs the car’s ignition system. It turns on when the correct key fob is used and the ignition lock is engaged. However, it’s common for the ignition switch to malfunction, particularly when the odometer reaches the six-digit range.

Multimeter equipment is a must-have for any DIY technician. It allows you to quickly inspect the state of the electrical connection and detect any potential issues.

Given that the ignition system encompasses more than just the ignition switch, this article will outline how to inspect every component and pinpoint the root of an electrical issue. A basic multimeter can do the job, but a broader range of test leads will make your task easier. You can choose the best option that suits your needs and budget from the list of possibilities provided below.

How To Test Ignition Switch (Step by Step)

To test an ignition switch, you can follow these steps:

  1. Prepare the necessary tools: You’ll need a multimeter (also known as a digital voltmeter), which is a device used to measure electrical voltage, resistance, and continuity.
  2. Locate the ignition switch: The ignition switch is typically found on the steering column, dashboard, or console area, depending on the vehicle make and model. Refer to your vehicle’s manual or online resources for the exact location.
  3. Disconnect the battery: For safety reasons, disconnect the negative terminal of the vehicle’s battery to prevent any accidental electrical shorts.
  4. Access the ignition switch: Depending on the vehicle, you may need to remove the steering column cover or other panels to gain access to the ignition switch. Again, refer to your vehicle’s manual for specific instructions.
  5. Identify the ignition switch terminals: The ignition switch will have multiple terminals or wires connected to it. They may be labeled or color-coded, but if not, you can refer to a wiring diagram specific to your vehicle.
  6. Test for power supply: Set your multimeter to the DC voltage setting. Touch the positive (red) probe of the multimeter to a known power source, such as the positive terminal of the battery or a constant 12V source. Then, touch the negative (black) probe to each terminal on the ignition switch. The multimeter should display a voltage reading close to 12V. If there is no voltage reading, it indicates a problem with the power supply to the ignition switch.
  7. Test for accessory position: Set the multimeter to the continuity or resistance setting. With the ignition switch in the “off” or “accessory” position, probe each terminal on the switch. There should be continuity or a low resistance reading between one terminal and the power supply terminal (usually labeled as “ACC” or “IGN”). If there is no continuity or a high resistance reading, it indicates a faulty ignition switch.
  8. Test for start position: Set the multimeter to the continuity or resistance setting. With the ignition switch in the “start” position (you may need to turn the key to this position), probe each terminal on the switch. There should be continuity or a low resistance reading between one terminal and the power supply terminal (usually labeled as “START” or “IGN”). If there is no continuity or a high resistance reading, it indicates a faulty ignition switch.
  9. Test for run position: Set the multimeter to the continuity or resistance setting. With the ignition switch in the “run” position (usually after the engine has started), probe each terminal on the switch. There should be continuity or a low resistance reading between one terminal and the power supply terminal (usually labeled as “RUN” or “IGN”). If there is no continuity or a high resistance reading, it indicates a faulty ignition switch.
  10. Reassemble and reconnect: Once you have completed the testing, reassemble any panels or covers that were removed to access the ignition switch. Reconnect the negative terminal of the battery.

It’s important to note that while these steps provide a general guideline for testing an ignition switch, the specific procedure may vary depending on the vehicle make and model. Always consult your vehicle’s manual or seek professional assistance if you are unsure or uncomfortable with performing the test yourself.

How To Change a Bad Ignition Switch

  1. Disconnect the battery terminals to cut off the power.
  2. Remove the bottom cover of the ignition column. If necessary, also remove the top cover.
  3. Disconnect the power wire from the ignition.
  4. Use a hex key, screwdriver, or socket to detach the whole ignition component if it needs to be removed.
  5. Alternatively, you can simply replace the ignition switch.
  6. Reconnect the battery terminals and power lines.
  7. Use the key to check the ignition.

In order to remove the cylinder lock, it may be necessary to replace the ignition key. However, if your current key and tumblers are still in good condition, there’s no need for this. To access a slot within the ignition system near the cylinder lock, use a narrow screwdriver. Insert the original key into the lock, and use your key to pry out the entire cylinder. Then simply repeat the process with the new assembly, and push the old cylinder back in.

Also Read: Car Jerks When Braking (9 Causes & Solutions)

How to Test Other parts of the Ignition System

If you suspect your ignition switch could be the root of your problems, testing it is a good idea. However, there are several other components of the ignition system that are also worth examining. This section will show you how to use a multimeter and other tools to test various system components.

Spark Plugs

The more time-consuming procedure is testing your spark plugs, but they are the components most likely to fail, so this should be done first. Spark plugs can be tested in two different ways, with the usual method involving removing them from the engine block. For this, you’ll need a specialized spark plug socket and a ratchet.

Disconnect the wires from the spark plug before unscrewing it with the socket. Once it’s been removed, there are two ways to test its functionality. One method involves reinstalling it into the wire, connecting a jumper wire to the ground and the spark plug thread, and then starting the engine. It’s functioning properly if sparks can be seen coming from the end of the spark plug.

The second method is safer and simpler. Set the multimeter to 20k ohm (or any setting in the tens of thousands) and use one probe to touch the tip of the spark plug and the other probe’s small tip to touch the base of the hook. By touching these two points, which are connected by a rod that runs through the center of the spark plug, you complete the circuit.

The value you get will be in thousands of ohms; however, the correct resistance range should be determined by consulting the owner’s manual or the manufacturer’s specifications for the spark plug.

If the spark plug has the correct resistance, turn the multimeter’s ohm setting to the maximum value, keep one probe on the tip of the spark plug, and touch the body of the plug with the other probe. If you get a reading while doing this, it means your spark plug is faulty, and you should discard it.

For consistency, you should replace the entire set of spark plugs if even one or a few are bad. While some engines use two spark plugs per cylinder, the number of spark plugs you need generally equals the number of cylinders in the engine.

Plug Wires

To test these, set your multimeter to the lowest ohm setting, and connect its probes to the inside of each spark plug wire. If there is no resistance, you’ll need to replace the spark plug wires for the engine to perform optimally. However, be careful to accurately measure the resistance and avoid accidentally connecting the probes inside the wrong places.

Ignition Coil

Attach the alligator clips to the two exposed towers of the ignition coil. This will make reading the multimeter easier, which should be set to ohms. To see if the ignition coil is within the limit and not defective, compare the value to your maintenance manual.

Crankshaft Sensor Position

You’ll need help checking your crankshaft sensor; consult the owner’s manual to find out what kind of value to look for. Insert both probes into the power jack, detach the crankshaft position sensor, and set your multimeter to the 200 v AC preset. While you’re watching the multimeter, have another person start the car.

If you’re confident that the values are incorrect, you can replace this crankshaft position sensor by pulling the old one out and pushing the new one into place.

Ignition Power Supply

The power distribution connector is typically located behind the ignition coil, though finding it can be a challenge. After disconnecting the wire, turn the ignition switch to the “On” position. Simultaneously, investigate the power source with the second multimeter probe while grounding the black wire and setting it to 20 v DC. A voltage reading indicates that the ignition is receiving power.

Final Thoughts

I would definitely advise purchasing a multimeter, even though it’s the most basic type since it’s an incredibly helpful tool for identifying power-related issues. I hope reading this article has made it easier for you to check your vehicle’s ignition switch and taught you ways to check the other parts of an ignition system.

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