Common Turn Signal Problems and Solutions

Having fully operating turn signals is important because the law states they must function properly on an automobile. Failure to use them for any reason can result in a citation and fine. More importantly it provides visual notification to drivers around you. Traffic accidents can be avoided when others fully understand where you are going.It’s frustrating when you try to do the right thing and signal other drivers, but they just don’t work. Often when a car is having turn signal problems it provides feedback to the driver. Sometimes it’s in the form of the light flashing too fast or too slow. This article will cover problems with the turn signal switch, bulbs and flasher. Included are common symptoms for specific malfunctions that can point towards failed components.

Turn Signal Flashers

A flasher is used by both the turn signals and the hazard lights. It is the component that’s responsible for turning on and off the individual bulbs. It accomplishes this using a temperature sensitive bimetallic strip that changes its shape when it reaches a certain temperature. When cool and in the relaxed position the metal strip completes the circuit allowing current to flow from the fuse panel through the switch and to the bulbs. This flow of current creates heat that eventually changes the shape of the bimetallic strip. When it bends the circuit is opened. The absence of current flow allows the strip to cool and the circuit is automatically closed restoring operation. This intermittent on and off interruption of current flow is what makes the bulbs flash. The location of turn signal flashers is dependent on the year, make and model of the vehicle. They can often be found in the fuse panel, but are sometimes by themselves. When the flasher turns on and off it makes an audible clicking sound. This can be used to trace down the location.

Turn Signal Switches

Although the lever to operate the turn signals is often on the left side of the steering column and can be reached from the steering wheel, the switch itself is usually located inside of the steering column. The lever reaches inside and moves the switch from the off position to close the circuit for the left or the right turn signal by moving the lever up and down.The automatic canceling function of a standard switch is operated by a cam that moves with the steering wheel. After the signal is activated and the turn is completed the steering wheel will return to the center position. During this process a cam will knock the switch into the center position turning off the flashing lights.

Turn Signal Bulbs

Turn signal bulbs are located in highly visible areas on the front and rear bumpers, plus some models will have side marker lights that will also flash. This provides even higher visibility and notification to others of your intentions. Signal bulbs can be single or dual filament bulbs that perform more than one operation. As an example a parking light can also flash as a turn signal bulb. In reality the parking light stays on and the additional filament inside that bulb is turned on and off by the switch and flasher.

Signal Flashes Fast

If a turn signal begins to flash faster or slower than normal this indicates a malfunction in the system. The physical reason for this is the resistance has changed in the circuit. The most common cause for a turn signal to flash too fast is a blown bulb. Performing a lighting maintenance check can often pinpoint the problem area. Malfunctions with the switch or wiring can also cause the bulb not to light, but these are less likely. For this reason mechanics will simply plug in a new lamp and retest operation to see if that was the problem.

Turn Signal Flashes Slow

If the turn signal flashes too slow or doesn’t flash at all, but the lights illuminate, it’s time to locate the flasher and perform some diagnosis. Some car manufacturers consider the flasher a module as they can be more complicated than just a simple bimetallic strip. If a turn signal flashes slow or not at all there could be a malfunction in this area. Mechanics will first verify all of the lights are working and then try swapping out the turn signal flasher with a new part to see if that restores proper operation.
When drivers are experiencing repeat failures on specific bulbs, it’s time to dig a little deeper and look for additional problems. Corrosion in the socket can cause high resistance and loose contacts can cause arcing that can damage the filament. Also moisture inside of the housing can accelerate corrosion and reduce the longevity of the lamp. Turn signal housings with moisture droplets inside should be removed dried and resealed.