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How to Test an Ignition Switch – What You Need To Know!

How to Test an Ignition Switch – What You Need To Know!

An ignition switch is as important as any part of the car. If you can control the ignition switch, you can control and access the whole car. It is the one responsible for sending an electric signal that allows you to start your car’s engine. It also activates the car’s stereo and power windows. The ignition switch or starter switch is generally reliable but a broken one can cause a lot of trouble. Your car may not start or if it does it immediately dies and it can also cause your car’s electrical components to stop working. If the problem becomes very serious, you might have to replace your ignition switch. But before you decide to do that, you need to know if it is really the ignition switch that is problematic. You have to assess it first and know how to test the ignition switch. 

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There are several methods you can try to test an ignition switch. You can use tools such as a test light, a voltmeter or a multimeter for these methods. But before that, let us explain first how it works and what you need to know before doing the procedure. Now, it has been established that the ignition switch supplies the voltage to the ignition control module and the ignition coil. The switch’s run terminal has two wires attached to it from the ignition system. One wire goes into the module and the other one creates a connection between the primary resistor and the coil. There is also another wire that connects the switch’s start terminal and the module. To test the ignition switch effectively, you need to check or inspect if all the connections to the switch are working and then you can proceed to remove the ignition switch from its slot. To make it easier for you to reconnect the wires after the test, you can use a masking tape to determine which wire goes to where. Once the ignition switch is removed, follow the steps below on how to test an ignition switch using different tools. 


Using a Test Light


  • Turn the ignition switch off and disconnect the module’s wire connector. Locate the starter solenoid’s S terminal and detach it. This stops the engine from cranking when you turn the ignition key to RUN position.


  • Turn the ignition key and put it to the RUN position. Test the voltage by using the probe on the red wire connection and on the ignition coil’s battery terminal. Turn the switch to START position and this time, probe the white wire connection of the module to test the voltage and also the ignition coil’s battery terminal. If there is no voltage from the tested parts, it means that your ignition switch is faulty.


Using a Multimeter


Testing the ignition switch using a multimeter can be done in several ways. 


  • Turn the ignition switch until you get to the OFF position. Using the positive lead of the multimeter, put the probe at the back of the power feed wire of the module and the negative lead into the ground base of your distributor. Turn the ignition key to the RUN position and measure the voltage using the multimeter. If your multimeter reads less than 90% of the  battery’s voltage, it is an indication that you have a faulty ignition switch.   


  • FInd the fuse panel under your steering wheel and open it. Take the starter signal’s fuse and inspect the metal strip carefully and thoroughly and check for damages or burns. If it is, replace the fuse with a functioning component with the same amperage. Get your multimeter and open your car’s hood. Turn the multimeter’s dial to the “volts” sign. Put its black lead to your vehicle’s frame or any of its unpainted metal part and the red lead on the battery’s positive terminal. The multimeter should read 12.6 V since it is the voltage of a battery that is in a good working condition. If the reading goes lesser than that, it means that the battery needs to be replaced. Turn the ignition key and try to start the engine. If it starts, your ignition switch is good and working. If it doesn’t, turn the ignition key to the RUN position. If it still doesn’t start and you can hear a ticking or clicking sound, it is an indication that your car’s issue is caused by something else and not by a faulty ignition switch. If it won’t start but there’s no clicking sound, then you need to replace your ignition switch because it is broken. 


  • Check the spark plug ignition first by removing one wire from the spark plug and placing the end of the spark plug wire close to a metal surface.Turn on the engine. If the spark plug is not faulty, you will notice a spark or a crackling noise. This indicates that voltage is getting through the spark plug. If there is no spark on the spark plug, it could mean that your ignition is malfunctioning. You can then check the voltage of the positive terminal when you turn on the ignition switch. Place the red lead of the multimeter on the positive terminal of the coil and the black lead on the negative battery terminal. Turn the ignition switch to the RUN position and check the reading of the multimeter. The positive terminal should have a reading, if it doesn’t have one or if the reading is too low, then there is a problem with your ignition switch or the ignition wiring. 


  • Another thing you can do is to find the ignition module’s positive wire and turn your ignition to the RUN position. Do not start the engine. Place the multimeter’s red lead through the module wire. If there is no multimeter reading, there must be an open circuit between the switch and the cable.


  • Get your ignition module’s negative wire and run it through the multimeter’s red lead. Remove the distributor cap without removing the spark plug wires. Turn on the engine and turn the distributor’s center shaft with your hands. As you start your engine, observe the distributor if it turns or not. If it doesn’t, you have a broken distributor. Check the multimeter’s reading. It should read zero or the battery’s actual voltage to determine that the distributor and the ignition switch are working fine. If it’s not, the whole ignition module needs to be checked or replaced. 


How do I know if I have a bad ignition switch?

Before taking any actions or maybe jumping into conclusions since you already know how to test ignition switches, you should also be aware of the symptoms of a faulty one. You can’t just go cracking or testing it without experiencing a symptom. Here some of the common signs of a bad ignition switch.


  • If you suddenly notice that something is off with your key movement. You can probably notice it every time you insert your key into the cylinder with the key and the ignition experiencing friction. This usually happens with old cars. This causes a worn cylinder over time if not fixed and your key might get stuck inside.  
  • Sudden halt of your vehicle. This is actually a common sign and usually the first sign of a bad ignition switch. This happens when a faulty switch cuts off the power supply to the ignition and the fuel system.
  • The stalling of your car just after starting it. You can experience this when your car is in the ON position and your switch fails. A power is supplied to the ignition system when you are cranking your engine but instantly ceases to function after that.
  • You encounter different switch positions when you turn the ignition key. The first one is the OFF position that you can spot just after you insert the key in the cylinder. Second is the ACC position when you turn the key a bit and you will notice the dashboard illuminating with the engine still turned off. If the dashboard light is still turned off after getting to the second position, you have a faulty ignition switch.
  • An overheating ignition can be a symptom too.    
  • When you turn your ignition key and the dashboard lights up but you hear no cranking sound. This can be caused by worn contacts inside the ignition switch. 
  • Dashboard lights are flickering while you are driving.
  • You encounter problems when you’re  trying to remove the key. Binding in the steering column lock can cause this to happen. You can try shaking the steering wheel lightly back and forth until you feel it click into a locked position. Try to remove the key again. If it doesn’t there might be a problem with its column locking mechanism. 
  • If your battery drains frequently, it could be the ignition switch causing it since it is responsible for turning on the car’s electrical system. This means that it is also capable of draining your battery. 
  • There is a mechanical lock for the steering wheel in the ignition switch. It locks your steering wheel to secure your car while it is parked. If you experience a stuck steering wheel, you will have to check the ignition cylinder and have it fixed.  


How to start a car with a bad ignition switch?

You now have an idea on how to test an ignition switch. But what if you are driving somewhere and you suddenly experience some of the symptoms of a faulty switch before you can even test it and you are stuck in a car that won’t start. Is there any way that you can bypass the ignition switch and start it? You can start it if you have the needed tools.


  • Hotwiring. This only works with older cars. Find the steering wheel column and remove the plastic cover that hides all the internal parts. Locate the wiring connector. Make sure you get the right one and not the other wires or cables. You can usually find it at the center of the steering column. Next is to find the ignition, battery, and starter connectors. Strip the battery wires an inch down from insulation and twist them together and connect the ignition wire to the battery wire. This time, the lights will turn on and so are the car’s electrical parts. Also strip the starter wire for about half an inch down and tap it on the connected battery wires to start the engine. 
  • Jumper Cables.  Open your car’s hood and find the ignition and battery. Get a jumper cable and connect the battery’s positive terminal to the coil’s positive side. This powers the car’s electrical system. Then find the starter solenoid and connect it to the battery’s positive terminal. Unplug the ignition switch wiring from the solenoid. Get a screwdriver and use it to short the solenoid’s positive terminal to the post that connects to the ignition switch. This can turn on the engine as the solenoid is activated. 



The ignition switch is something you cannot take lightly since it probably is the most used switch on your car. It also needs service as it is at risk of wear and tear like any other parts of a vehicle. A bad ignition switch can cause a lot of problems, each is associated with different symptoms. The problem varies depending on what was damaged. It could be the broken springs, worn switch contacts, or even temperature problems. It is fortunate that we can learn how to test an ignition switch and troubleshoot it on our own. Just make sure to do the process correctly. Learning the basics of reading electrical diagrams can help too. You can always check your car’s repair manual. There is a section there that covers the power distribution and the ignition switch diagrams which can help you find and locate faulty electrical components. Of course, basic understanding on these things is a must. If you feel like you are stuck somewhere, do not be reluctant to ask for professional help.