Home CAR GUIDE ELECTRICAL SWITCHES Car Ignition Switch Guide

Car Ignition Switch Guide

Most drivers think of the ignition switch like a slot where they insert the key to start their car, but that’s actually the ignition lock cylinder. The ignition switch is a complex electrical component that has to “read” anti-theft coding in the key before it activates the electrical systems in the vehicle so the vehicle can start or allow an automatic transmission to be shifted out of Park. On vehicles having push-button start, the ignition switch has to recognize the anti-theft code transmitted by the key fob before it will allow the engine to start.

If nothing happens when the key is turned in the ignition lock or if no dashboard lights come on when it’s turned to the On position, those are the signs showing that the ignition switch has failed or there’s a problem with the wiring from the switch to the starter or other electrical components. These could be the signs of other problems, such as a failed starter motor or a dead battery too.

Another potential issue is that a heavy key ring can cause wear on the lock cylinder and the ignition switch, making the switch to turn to the Off position when a car hits a bump or pothole and disabling the power-steering, air bags as well as other systems. That’s the reason that led to General Motors recalling 2.6 million vehicles in 2014 to replace the ignition switch, lock cylinder and keys.

Although there are many types of ignition systems on the market today, most can be placed in one of the three groups: the conventional breaker-point ignition (in use from the early 1900’s), electronic ignitions (popular since the early 1970’s), or the distributor-less ignition (came in the mid-1980’s). Here’s an overview on how each of these systems function-

Conventional Break-Point Ignition System

  • Older style of ignition system – It is no longer used on modern cars in the U.S.
  • This system uses points, distributor as well as an external coil.

An automotive ignition system is divided into two electrical circuits, i.e., the primary and secondary circuits.

  1. The primary circuit has the function of carrying the low voltage. This circuit operates only on battery current and is controlled through the breaker points and the ignition switch. When the ignition key is turned on, a low voltage current from the battery flows across the primary windings of the ignition coil, through the breaker points and back to the battery. This current flow makes a magnetic field to form around the coil.
  2. The secondary circuit has secondary windings in the coil, the high tension lead between the distributor and the coil (commonly called the coil wire) on external coil distributors, the distributor cap, the distributor rotor, the spark plug leads as well as the spark plugs. As the engine rotates, the distributor shaft cam keeps turning until the high point on the cam causes the breaker points to separate suddenly. Instantaneously, when the points open (separate), current flow stops flowing through the primary windings of the ignition coil. This makes the magnetic field to collapse around the coil. The condenser takes the energy and prevents arcing between the points each time they open. This condenser aids in the rapid collapse of the magnetic field too.
  3. The line of flux in the magnetic field makes a cut through the secondary windings of the ignition coil, creating a high voltage which is high enough to jump the gaps in the middle of the rotor and the distributor cap terminals, and the electrodes at the base of the spark plug. Assuming that the engine is properly timed, the spark reaches the air-fuel mixture in the cylinder and also when the combustion begins.
  4. As the distributor keeps rotating, electrical contact between the rotor and distributor cap terminal is broken, stopping the secondary flow. At the same time, breaker points close the complete primary circuit, making primary current to flow. This primary current will then again create a magnetic field and the cycle is repeated for the next cylinder in the firing order.

This process happens in a few milliseconds. In fact, it takes place approximately 18,000 times per minute at 90 miles per hour.

Electronic Ignition System

  • The requirement for higher mileage, reduced emissions and greater reliability has led to the development of the electronic ignition system.
  • This system still has a distributor, but the breaker points have been replaced with a pickup coil, and there’s also an electronic ignition control module.

Like conventional ignition systems, electronic systems got two circuits: a primary circuit and a secondary circuit. The entire secondary circuit is the same like in a conventional ignition system. In addition, the section of the main circuit from the battery to the battery terminal at the coil is the same as in a conventional ignition system.

With the ignition switch is turned on, primary (battery) current flows from the battery through the ignition switch to the coil primary windings. Primary current is turned on and off by the action of the armature because it revolves past the pickup coil or sensor. As each tooth of the armature nears the pickup coil, it makes a voltage that signals the electronic module to turn off the coil primary current. A timing circuit in the module will turn the current on again after the coil field has collapsed. When the current is off, however, the magnetic field built up in the coil is made to collapse, which leads to a high voltage in the secondary windings of the coil. It is now functioning on the secondary ignition circuit, which is the same as in a conventional ignition system.

Distributor-less Ignition System

  • It’s the newest type of ignition system.
  • It is very different from conventional and electronic as coils sit directly on top of the spark plugs, no spark plug wires, and the system is electronic.

The third type of ignition system is your distributor-less ignition. The spark plugs are fired directly through the coils. Spark plug timing is controlled through an ignition module and the engine computer. The distributor-less ignition system might have one coil per cylinder or one coil for each pair of cylinders.

There are several different advantages of not having a distributor:

  • No timing adjustments.
  • No distributor cap and rotor.
  • No moving parts to wear out.
  • No distributor to accumulate moisture and cause starting problems.
  • No distributor to drive thus providing less engine drag.

5 Common Ignition Switch Problems and How to Fix Them

Like most drivers, you likely don’t think much of the complex series of steps that occur when you get in your car and drive away each morning. Putting the key in the ignition switch and then starting the car feels like second nature. However, if your car has ignition switch problems, you might not be able to start the car at all. Ignition switch problems can also cause issues on the road, like unexpected shutdowns or electrical problems.

Ignition switch problems are no fun, especially if they’re stopping you from getting to work or school or play. If you have an ignition switch problem, taking care of it right away will prevent you from being stranded. Here’s how to fix some common issues.

1) Wrong Key, Wrong Car

The average car key has only a few hundred thousand combinations. If an automaker sells 200,000 cars per year, there are pretty good chances that you could unintentionally unlock someone else’s car door, especially when you consider that car door cylinders have fewer tumblers than ignition cylinders, which means fewer combinations. 

Of course, if you access to the car itself with your key, you won’t be able to turn on the ignition because of all those extra tumblers. And on the off chance that you do turn the ignition cylinder, the immobilizer won’t help you to start the car as it’s protected by one-in-millions of transponder codes.

How to Fix ItEnsure you’re actually trying to start your own car! This has really happened, much with the chagrin of car owners and inadvertent felons.

2) Steering Wheel Binding

The ignition cylinder is mechanically connected to the steering wheel lock, to make sure potential thief cannot steer the car without the key. If you turn off the engine with the steering wheel turned or turn the steering wheel after turning off the engine, the steering wheel lock can bind and stop you from turning the ignition.

How to Fix It: Fortunately, this is quite an easy fix. Just turn the wheel back and forth until and unless the ignition cylinder is freed.

3) Worn Key or Ignition Cylinder

It’s a fact of life that mechanical things tend to wear out, and the same is for mechanical keys as well as with key cylinders used in your car’s ignition system. You might insert and remove the ignition key thousands of times every year, wearing the key and tumblers ever-so-slightly every time. Heavy key chains can add more stress to the ignition cylinder resulting in increased wear. After a while, the key might fall out of the cylinder or be unable to turn out of the lock position or, an unworn key might not turn a worn ignition cylinder, as they haven’t “worn together.”

How to Fix It: The best way to do this is to getting a new lockset, with new keys and a new cylinder. You should think of getting a matched lockset that includes the door and trunk cylinders.

4) Ignition Switch Fault

The ignition switch itself is connected to the ignition cylinder through a shaft or lever. Inside the ignition switch, several contacts connect important electrical systems required to start and run the car. Generally speaking, in the “OFF” position, the ignition switch doesn’t connect to anything; in the “ACC” position, the radio or fan might be energized; in the “RUN” position, the engine control module is energized; and finally, in the “START” position, the starter relay is engaged. (These generalizations will depend significantly on year, make, and model.)

Worn ignition switch contacts, temperature problems, or broken springs can all lead to the ignition switch to fail, preventing you from starting your car. On the road, poor ignition switch contacts can shut the engine off while driving, which could be quite dangerous.

How to Fix It: After making sure the rest of the electrical system is intact, such as fuses, relays, and circuits, just replace the ignition switch.

5) Immobilizer Problems

Modern cars with immobilizers utilize transponder keys to enable or disable engine starting or running. The chip in the key gives a specific code, of which there are millions. If this code matches exactly to the ones programmed into the vehicle, engine starting is enabled. An incorrect key code like one from an unprogrammed key or damaged key, would stop the engine from starting. Code “confusion,” such as having multiple keys can also take place, preventing ignition. Electrical problems, such as broken immobilizer antenna wiring, which mostly encircles the ignition cylinder, can prevent the engine immobilizer from reading transponder codes. Finally, some keys consist of battery-amplified transponders, so a dead battery might prevent the codes from being read.

How to Fix It: For amplified transponders just replace the battery. Otherwise, you might need to have a professional make sure all keys are programmed to your immobilizer and that the system is electrically sound.

Video of How to Replace Ignition Switch in Your Car

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