How to Test an Ignition Switch Using a Multimeter

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An ignition switch is found in the control system of a vehicle, and its primary purpose is to activate the vehicle’s electrical system, including the power window and the stereo. It is also known as a start switch or a starter switch. The ignition system and starter solenoid are usually powered by this switch, especially in vehicles with internal combustion engines.

​​Testing Using a Multimeter

A faulty ignition switch can cause a lot of troubles and inconvenience vehicle users. Before concluding that you have a malfunctioned ignition, here are some headlights to look out for.

  1. The car stops suddenly
  2. The car refuses to start
  3. The vehicle stalls right after starting
  4. You are having difficulties when powering up your accessories.

Without your ignition switch, you cannot start your engine. In some cars, install the switch as part of an anti-theft system. It is, therefore, advisable to use a multimeter to test whether your ignition switch is working because it will check for both AC and DC voltage, current and resistance.

Outlined below are several methods you can use to test the functionality of your ignition switch using both a digital and an analog multitester.

Method 1

Step 1

Under your steering wheel, locate your fuse panel and open it. Using your fuse pullers situated on the panel, pull the starter signal’s fuse.

Step 2

After completing the first step, Carefully and closely examine the metal strip and ensure it is not damaged or burned. If the fuse is damaged, replace it with a functioning component of similar amperage as the previous one.

Step 3

Turn the dial on your DMM (Digital Multimeter) to the “volts” sign after opening your vehicle’s hood. Place the black lead on your multimeter to the frame of your car, and the positive terminal on your battery, attach red lead of your multitester. For a well-functioning battery, the voltage reading on your voltmeter should be 12.6 V.

If the text is less than 12 volts, your battery needs replacement because it is dead. Start your engine by putting the ignition key into your ignition switch. You know that the ignition switch is working well if your engine starts properly.

If your engine does not start, turn the ignition key to the (III) position. If it does not start, but you hear a clicking sound, your vehicle has a problem, but it is not with the ignition switch. If you do not hear a clicking sound when the key is at (III), and the engine does not crank, the ignition switch is broken, and you need to replace it.

Method 2

Step 1

From the spark plug, remove one wire and thrust an old spark plug all through to the end of the plug boot. Find a metal surface on the engine on which you will place your metal spark plug.

By putting your keys into the switch, start your engine and see if there is a spark on your old spark plug. If no spark appears on the plug, your ignition is definitely faulty.

Step 2

Using your multimeter, check for the voltage of the positive terminal when the key is in the switch, and the ignition switch is on. On the positive terminal of the coil, place the red lead. On the negative battery terminal, place the black lead of the voltmeter.

Place the ignition switch to the run position after turning it on. The voltage of the battery should be reading at the positive terminal if the ignition switch is working effectively. If there is no voltage reading, or the reading is too low, there is a problem with the ignition wiring or the ignition switch.

Step 3

Locate the positive wire of the ignition module and rotate the key to the ‘run’ position. After this activity, do not start the engine. Hold the multimeter’s red lead and push the module wire through it.

Note the battery’s voltage is reading at the wire. If there is no voltage reading, there is possibly an open circuit between the switch and the cable.

Step 4

Find the negative wire of your ignition module. Run the negative wire through the red lead of the multimeter. Without taking out the spark plug wires, remove the cap on the distributor. Start your engine, or rotate the center shaft on your distributor using your hand.

Observe the distributor rotor keenly as your engine is starting. It the rotor does not turn, the distributor or the gears are dysfunctional. At this point, the multimeter should be reading zero or the battery’s voltage if the ignition switch and the distributor are working. The entire ignition module should be changed if the multi tester does not show the correct voltage.

Method 3

Step 1

Ensure your multimeter is working by turning resistance to “XI.” This step takes place after turning on the multimeter and selecting the ohm (Ω) function. If the resistance is zero, the VOM is functioning. It is, however, not necessary to go through this step if your meter has an auto-range capability.

Step 2

Rotate the ignition key till you get to the off position. Place your multimeter’s positive lead to the back of your ignition module’s power supply wire. To the ground base of your distributor, place the negative lead.

Step 3

Using your multimeter, measure your battery’s voltage. Ensure your key is at the run position on the ignition switch. If the reading on the multimeter is less than 90% of the battery’s voltage, your ignition system is faulty.

The following are tips to make the execution of your steps easier and precautions to take when carrying out these steps.

  • Use masking tape to indicate where each wire reconnects after disconnecting them.
  • Turn off all circuit breakers that feed power to the switch, to avoid electric shock.
  • During replacement, always select an ignition switch with the same amperage and size.
  • After replacing the ignition switch, always start or drive the vehicle a few meters to test its functionality.

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