Why is My Turn Signal Blinking Fast? (Here's How to Fix It)

From time to time, drivers encounter unfamiliar vehicle issues that raise questions. One example is when a turn signal flashes rapidly on one side but not the other.

While relatively common, the root cause of this fast blinking turn signal can be confusing. In reality, it may indicate several different issues. Read on to learn what can cause this and how to fix it.

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Common Causes of a Turn Signal That Flashes Fast

While diagnosing a fast blinking turn signal bulb is generally considered to be a rather straightforward procedure, attention to detail remains paramount. A condition of this nature can be caused by one of several different underlying issues.

The following are several of the most common causes of a fast blinking turn signal.

Faulty turn signal bulb
Improperly selected turn signal bulb
Compromised flasher module
Damaged turn signal wiring or socket
Hyper flashing induced by a recent upgrade to LED bulbs

See Also: Pros/Cons of Xenon Lighting

How to Fix a Turn Signal That’s Blinking Fast

When attempting to fix a turn signal that blinks rapidly, one must first determine the root cause of the issue at hand. By following the steps below, you will be able to quickly diagnose your vehicle’s lighting fault, thereby allowing you to quickly remedy that which proves problematic.

#1 – Check Turn Signal Operation

When attempting to determine the root cause of a turn signal-related issue, it is important to conduct a quick walk around of your vehicle.

After toggling your turn signal switch to one direction or the other, verify that both the front and rear turn signal lights of this side function as expected. Then, repeat this process with the turn signal switch engaged in the opposite direction.

#2 – Check Power/Ground To Inoperable Lights

If any turn signal lights are found to be inoperable, it is important to check for proper delivery of power and ground at the corresponding plug. This can be done by removing the bulb in question and probing the prongs of the receptacle with a test light.

With the clamp end of the test light connected to a ground, one prong of the bulb receptacle should prove hot, thereby illuminating the test light. Likewise, contact with the other prong of the receptacle should illuminate the test light, when the light’s opposite end is attached to a 12-volt power source.

#3 – Replace Faulty Bulbs

If an inoperable turn signal bulb was found during “step 1”, yet proper delivery of power and ground was verified, a new bulb should be installed. After installation has been completed, verify that the bulb illuminates and flashes as expected.

In the majority of cases, this will also restore the flashing of all turn signal bulbs to their normal pace.

#4 – Replace Flasher Relay (If Necessary)

If your vehicle utilizes standard non-LED bulbs, yet the replacement bulb replacement does not remedy your concerns, a bad turn signal relay becomes suspect. This module can be sourced from almost any auto parts store, and can typically be purchased for a rather reasonable price.

The installation of this relay is also generally no more difficult than replacing a fuse. However factory-specific service literature should be consulted when attempting to locate the module in question.

#5 – Correct Resistance Related Issues

If you have recently replaced your vehicle’s standard turn signal bulbs with replacement LED turn signal bulbs, then it is a good chance that you are encountering resistance related issues.

Since a vehicle’s flasher module relies upon resistance within the circuit for proper operation, the installation of low-resistance LED bulbs can cause a flasher to cycle rapidly, as if a bulb’s filament was open.

To correct this condition, specialty inline resistors can be purchased and installed, thereby restoring a flasher module’s tropical operating characteristics.

How to Reset a Fast Blinking Turn Signal

To reset a fast blinking turn signal, you’ll need to address the underlying issue causing the rapid blink rate. Fast blinking is typically a sign that one of the turn signal bulbs has failed or there is an issue with the electrical circuit. Here’s what you can do:

Check and Replace Bulbs: Inspect the turn signal bulbs on the side that’s blinking rapidly. Replace any bulbs that are not working or that appear dimmer than usual. After replacing the faulty bulb, the turn signal should return to its normal blinking rate.
Inspect the Bulb Sockets: If the bulbs are fine, check the bulb sockets for corrosion or damage, which can cause a poor connection and lead to fast blinking. Clean or repair the sockets as needed.
Check for LED Issues: If your vehicle has LED turn signals or if you’ve upgraded to LED bulbs, the fast blinking could be due to the lower resistance of LEDs. In this case, you may need to install load resistors to balance the circuit or replace the flasher relay with one that is LED-compatible to return the blink rate to normal.
Inspect the Turn Signal Relay: If the bulbs and sockets are in good condition, the issue may be with the turn signal relay or flasher unit. Locate the relay (usually found in the fuse box) and replace it if necessary.
Check the Wiring: If none of the above solutions work, there may be a wiring issue. Inspect the wiring for any signs of damage, wear, or loose connections and repair as needed.

How Do Turn Signals Work?

To understand the cause of a rapidly blinking turn signal, one must first grasp the basic principles of turn signal operation. A vehicle’s turn signal circuit is provided power through a fused hot wire, which most often originates within the underhood junction box.

This hot wire delivers power through a flasher module to the turn signal switch, located along the vehicle’s steering column. When a driver toggles the turn signal switch upward or downward, the circuit is completed, thereby sending power to both the front and rear turn signals for the side of the vehicle that has been selected.

Instead of sending constant power to these bulbs, power is momentarily interrupted, as it is directed through the circuit’s flasher module. This module uses a heat-sensitive contact, which expands/contracts, effectively making and breaking connections.

The flasher module operates off of the principle of resistance, which is impacted upon the circuit as power is transferred to a turn signal bulb’s filament.

By design, a broken filament within a turn signal bulb reduces this resistance, thereby causing the flasher module’s operation to speed up, which in turn causes the remaining bulb to flash at a much faster rate.

Is a Fast Blinker Illegal?

The issue of whether or not a fast blinker is illegal is largely open for interpretation. The Department of Transportation specifies that a vehicle’s turn signal is not to exceed a rate of 120 blinks per minute. However, individual state laws might present an even lower acceptable maximum threshold.

As a result, the legality of hyper flashing is largely dependent upon the exact speed of flashing as it occurs, and the state in which one is driving.

At the very least, hyper flashing can draw additional scrutiny from law enforcement. This stems from the fact that the rapid strobing of a hyper flashing turn signal can be quite distracting to fellow motorists.

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Josh Boyd

Josh has worked as a full-time mechanic for over 12 years, with 6 ASE (Automotive Service Excellence) certifications under his belt. He began his career as an automotive technician at local Toyota dealership and has since transitioned to specializing in diesel trucks and equipment.

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