How To Test Ignition Switch – Two Different Methods

A dysfunctional ignition switch can cause plenty of troubles. It may result in some electrical components stop working, the car does not start or dies immediately after being started. You may need to replace the switch if the problem becomes severe or the car does not respond at all. But, you have to know how to test ignition switch to determine that it actually is broken and needed to be fixed.

Symptoms Of A Failing Ignition Switch

Know about the symptoms before jumping into the conclusion that you need to replace the component or learning how to test ignition switch. A faulty switch will show these signs to warn about a potential issue.

Sudden Halt Of The Vehicle

It is the primary sign that the ignition key is failing. If the failure occurs when the engine is running, it may cut the power to the ignition and fuel system, resulting in the stalling of the car.

Car Stalls After Starting

It happens when the switch fails in the ‘ON’ position. It may supply power to the fuel and ignition systems when the engine is cranking but stops functioning immediately after.

how to test ignition switch
A failing ignition system will show various signs. (Photo Source: honda-tech)

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Trouble Powering Up The Accessories

Turning the key to the ‘acc’ position is likely to power up the accessories. When it does not happen, there must be a problem with it.

How To Test Ignition Switch: The Procedure

The function of this component is to provide voltage to the ignition control module and ignition coil. The ignition system has two wires attached to the switch’s run terminal. One goes into the module and the other establishes a connection to the primary resistor and coil. The switch’s start terminal also has a wired connection to the module.

To examine the ignition switch, you have to remove it from its slot and check the resistance and continuity all along the terminals. Before the removal, it is necessary to examine whether the connections to the switch are working.
You can check the voltage of the switch by using two tools – a 12-volt test light or a digital multimeter.

How To Test Ignition Switch With A Test Light

Step 1: Disconnect the module’s wire connector after turning the ignition switch off. Also, disengage the starter solenoid’s S terminal. Doing so will stop the engine from cranking despite turning the ignition key to the run position.

Step 2: Rotate the ignition key and place it to the run position. Probe the red wire connection to test the voltage. Do the same at the ignition coil’s battery terminal.

Step 3: Then, rotate the switch to the start position and probe the module’s white wire connector and ignition coil’s battery terminal to examine the voltage.

The circuit and the switch are faulty if there is not voltage.

how to test ignition switch with multimeter
Using a multimeter is hassle-free. (Photo Source: mightyguide)

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How To Test Ignition Switch With Multimeter

Turn the ignition key to the off position. Use the positive lead of the multimeter to back-probe the module’s power feed wire. The negative lead should go into the distributor base’s good ground.

Now the key has to go to the run position and you have to measure the voltage with the meter. Anything less than 90% of the battery voltage indicates a trouble with the ignition system.