Turn Signal Switch Problems

Once upon a time, drivers relied on hand signals to notify other people on the road of their intention to stop or turn their vehicles in a certain direction. While certainly dated, knowing basic hand turn signals can be helpful—especially if your turn signal stops working.

Naturally, a broken turn signal switch means you will no longer have control over your turn signal lights. And while your vehicle will remain drivable, you lose the easiest and safest way to communicate your intentions on the road with other drivers.

Symptoms of a Bad Turn Signal Switch

A turn signal switch should last the life of the vehicle. However, there are instances where the switch may fail because of manufacturing defects, rough use, spilled coffee, or other reasons.

Common symptoms of a bad turn signal switch include:

Turn signal lamps don’t work at all

If your turn signals don’t work at all, the turn signal switch may be faulty. Of course, the problem has many other potential causes as well, so you’ll want to do some troubleshooting before condemning the switch.

For example, the issue could also be a result of a blown fuse, a faulty flasher unit (older vehicles), or a problem with the BCM (newer vehicles). Bad grounds, wire connections, and other issues might also be the problem.

Only one side of the turn signal lights is working

When you activate the turn signal switch, its internal contacts close, providing a path for electricity to activate the turn signal lights on one side of the car. As such, it’s possible for a failed switch to prevent electricity from reaching either the left-hand or right-hand turn signal lights.

Other car systems don’t function properly or at all

Many turn signal switches also bear the controls for other car systems. Issues with the lever can affect those switches, causing fog lights and other components to stop responding to their control knobs.

Even if your turn signal system works fine, you may still need to replace its switch to keep other car systems in top condition.

What is a Turn Signal Switch?

Also known as blinker switch, turn signal lever, or turn signal arm, the turn signal switch is a lever that’s usually mounted on the steering column. Pressing down on it engages the left signal while pushing it up activates the right signal.

Meanwhile, pulling the lever towards you changes the headlamp settings.

On older vehicles, power routes to the turn signal switch through a flasher unit. The flasher contains a switch that opens and closes the circuit to the turn signal switch, causing the turn signals to flash when activated. The flasher is also responsible for the clicking noise you hear when activating the turn signals.

Meanwhile, on newer vehicles, a computer, which is often referred to as the body control module (BCM), manages the turn signals. When the driver operates the turn signals, an electrical signal is sent to the body control module (BCM). The latter then activates (or tells another module to activate) the turn signal lights and perform flashing duties.

Most modern vehicles also have some way of emulating the sound made by a traditional turn signal flasher, as drivers still expect to hear that sound when activating the turn signals.

It’s also important to note that the switch usually controls more than just the turn signal lights. It may also manage the dials and switches, or some of the other car systems. Depending on the model and turn signal switch design of your car, you may have access to cruise control, headlights, fog lights, or windshield wipers.

Because of this, the turn signal switch is sometimes referred to as a combination switch.

Diagnosing Turn Signal Switch Problems

Turn signal circuits are complex—especially on modern vehicles. To diagnose the switch, you’ll want to use a digital multimeter (DMM) to ensure that, when the turn signals are engaged, power is making it through the switch.

Of course, testing the switch is easier said than done. Accessing the appropriate points to test the turn signal circuit can be difficult. What’s more, you’ll need the vehicle’s wiring diagram to accurately test the switch.

For these reasons, it’s often best to have a professional inspect your car’s turn signal switch. Only attempt your own evaluation if you possess extensive experience and confidence in your automotive know-how.

Can You Drive with a Bad Turn Signal Switch?

While it will not really prevent you from operating your vehicle, your vehicle’s turn signal switch contributes to your safety and the safety of other drivers on the road.

Except in emergencies, it is not advisable to drive if it’s not working properly. Get the problem fixed as soon as possible to promote a safe driving experience.

You can also use old-fashioned hand signals, as previously mentioned.

Turn Signal Switch Wiring

Many newer model vehicles don’t have their turn signals wired through the switch. They typically send a request to a body control module or a lighting control module or some other such module on the vehicle and the module does the heavy lifting. Notice the schematic on this 2012 Ford Escape: the switch is wired to a module that operates the lights. The flasher function on a system like this is built into the module.

However, there are vehicles that do use a hard-wired turn signal switch; you need to be sure you know what kind of switch you have.

Many vehicles now have what is known as a “combination switch” or “multifunction switch” that handles wiper function as well as turn signal operation.

Understanding the basic wiring of a turn signal system is important. Unless the turn signals and stoplights are separate bulbs (and sometimes they are), the stop lamp switch is part of the circuit so the turn signal function can blink one light or the other while the brakes are applied. For that reason, a faulty turn signal switch can cause the stop lights not to work particularly if the high mount stop light works but the regular stop lights don’t.