(Updated on December 28, 2020)
Every day, we rely upon our vehicle to start when commanded to do so, as we insert our keys into the ignition, and turn the ignition switch. Unfortunately, like any other automotive component, ignition switches do wear out on occasion. When this occurs, the severity of that which is experienced differs from case to case.
The truth is, not every ignition switch fails in the same manner. While some motorists experience major operational issues, others are left with a series of curious issues, which they would be highly unlikely to attribute to an ignition switch failure.
Read on to learn more about how an ignition switch works, and the symptoms associated with ignition switch failure.
How Does an Ignition Switch Work?
An ignition switch is directly responsible for distributing voltage as required for vehicle starting, as a motorist turns their ignition key. A vehicle’s ignition switch is fed direct supply voltage from a vehicle’s battery, which is then distributed to various circuits as each keystroke position is reached.
An ignition switch generally features three individual keystroke positions. The first of these three positions generally provide power to a vehicle’s electrical systems. The second position supplies voltage to the vehicle’s fuel and ignition systems.
Finally, the third and final keystroke position engages the starter by charging the ignition circuit’s exciter wire. As the vehicle’s engine turns over, the driver returns their key to the ignition switch’s second position.
Bad Ignition Switch Symptoms
As previously mentioned, a bad or failing ignition switch can produce a broad range of symptoms, many of which can prove puzzling to the average motorist. The first step to eliminating your ignition switch woes is to recognize the telltale signs of such a failure.
The following are the 5 most common symptoms associated with a bad or failing ignition switch.
The electrical contacts found within a vehicle’s ignition switch have a tendency to wear with time. When this occurs, it can be quite difficult for an aging ignition switch to supply the proper amperage and voltage required for proper circuit operation, on a consistent basis.
Stalling is most often experienced while cruising or within seconds of startup.
Many motorists overlook stalling as a symptom of an ignition switch failure, due to the fact that their vehicle started as intended when commanded to do so by the switch. However, in reality, the ignition switch itself has actually experienced a failure in its “On” position.
As a result, the supply voltage is provided to the ignition system and fuel pump when switched to the “Crank” position but drops this voltage as soon as cranking is complete.
2) Failure to Start
When an ignition switch experiences a failure in the “Crank” position, it can be impossible to start your vehicle. This is most commonly characterized by a lack of response from the engine’s starter when the key switch is turned all the way over. In this case, no audible noise will be heard from the vehicle’s starter.
When failed in this manner, an ignition switch is unable to distribute voltage to the vehicle’s starting solenoid, via the circuit’s exciter wire. Without this signal, no energization of the starter will occur.
This is one of the most common symptoms related to ignition switch failure, although such issues are often misdiagnosed as a bad starter.
3) Failure to Power Accessories
If an ignition switch were to fail at its first keystroke position, one could expect to experience a lack of accessory drive function. While this is not as common of a failure as those mentioned prior, an ignition switch can certainly be the cause of such symptoms.
It is also possible for lighted accessories to flicker, or operate in a dim fashion, due to excess resistance within the accessory sector of the ignition switch.
While some motorists will shrug off such seemingly minor concerns, doing so is certainly not advised. If an ignition switch has failed at one keystroke position, there is a reasonable chance that additional failure could follow shortly, perhaps leaving you stranded in the process.
4) Key Will Not Turn
Another symptom of a failed ignition switch relates to a sudden inability to manipulate a vehicle’s lock cylinder with your key. If you find that you can no longer physically turn over your ignition, it is highly probable that the ignition switch’s internal tumblers have failed, thereby requiring replacement to restore proper function.
In some cases, a vehicle’s ignition lock cylinder can be replaced without actually replacing the system’s electronic switch. On others, however, these two components come as an assembly and must be replaced in tandem.
The exact service procedure for ignition switch replacement differs from one vehicle to the next and can be located by consulting factory-specific service literature.
See Also: How Does Keyless Entry Work?
5) Intermittent Anti-Theft Light
If your vehicle features a decoder key, then the first sign of a failing ignition switch might be the intermittent display of an “anti-theft” light when attempting to start the vehicle.
Many newer styles of ignition switches feature a decoded, which is capable of recognizing a vehicle’s key. When one attempts to use an incorrect key, the vehicle electronically disables various critical functions.
In this case, testing of the vehicle’s remote battery strength will need to be conducted to rule out issues regarding a driver’s key fob. Additionally, some issues of this nature can be remedied by simply reprogramming the key in question with the ignition interlock’s decoder.
Ignition Switch Replacement Cost
The cost of having a vehicle’s ignition switch replaced can vary significantly, from one make and model to the next. However, one can quite easily figure up a ballpark estimate for such a repair.
To do so, you must add the estimated cost of the ignition switch itself, to the estimated labor cost associated with replacement.
Most OEM-grade ignition switches can be purchased for $50 to $250, though some cost considerably more in extreme cases. The vast majority of ignition switches can be replaced in 1-2 hours. As a result, consumers can expect to pay $75-$200 in labor costs.
When factoring these numbers together, one can expect to pay between $125 to $450 to have their vehicle’s ignition switch replaced.
Related: Ignition Coil Replacement Cost
How to Bypass the Ignition Switch to Start a Car
If your car’s ignition switch has failed, and you are simply trying to get home, or attempting to get your vehicle dropped off at the shop, then a quick bypass is in order.
Assuming that your ignition switch has failed at the “crank” position, which is often the case, then a push button jumper can be wired between a 12v positive source and the starter solenoid’s positive stud.
A push-button starter switch can be purchased at virtually any parts store for a nominal cost. Most even feature a built-in fuse or circuit breaker to prevent load related issues.
If a particular switch that has been purchased does not feature any form of circuit protection device, it is advisable to wire up a fuse holder inline with your push-button starting switch or jumper.
Prior to firing up your vehicle, place your key in the “On” position within the ignition. This provides power to the engine’s fuel pump, injectors, and ignition circuitry. With this step complete, the simple push of a button should be all that is needed to bring your vehicle back to life.
How to Test an Ignition Switch
An ignition switch can be tested by verifying output at each wire, with the use of a multimeter. The following steps will assist you in doing so.
- Using a back probe, gain access to each wire that is integrated into the ignition switch wiring harness.
- With the key in the off position, use your meter’s positive lead to find the input wire that is delivering 12v to the switch, while holding the black lead to a known ground.
- Next, turn your vehicle’s key to the accessory position, while checking to see if 12v has now been distributed out of the switch on a dedicated wire. If so, the switch’s accessory circuit has proven viable.
- Repeat step #3, with your key turned to the “On” position. If favorable results are achieved, then the power circuit has proven viable,
- Repeat step #3 while holding the key in the “crank” position. If favorable results are achieved, then the ignition switch’s cranking circuit has proven viable.
- If your ignition switch failed any of the abovementioned tests, it should be discarded and replaced. If all tests were passed, then the switch in question is free of defects.