Turn Signal Flashing Fast? Here's How to Fix It
That rapid clicking from your blinker is called hyperflash. Your car is telling you something is wrong with the circuit. Good news: it's almost always one of two things, and both are easy to fix yourself.
Why the Flasher Relay Speeds Up
The flasher relay controls your turn signal blink rate. It works by measuring the electrical load (resistance) in the circuit. A normal incandescent bulb draws a specific amount of power. When the relay sees that expected load, it blinks at the standard 60 to 120 times per minute.
When the load drops lower than expected, the relay speeds up. This was designed on purpose. A burned-out bulb means less resistance in the circuit. The faster blink rate is a built-in warning: one of your lights is out. Without it, you might drive for weeks with a dead turn signal and never know.
The problem is that modern LED bulbs draw much less power than the incandescent bulbs the relay was designed around. To the relay, a working LED bulb looks like a burned-out incandescent. So it blinks fast even when all your LED lights are functioning perfectly.
Cause 1: A Burned-Out Bulb
If your turn signals use regular incandescent bulbs and suddenly one side starts blinking fast, start here. A burned-out bulb is the most common cause.
Check both the front and rear turn signal on the fast-blinking side. Walk around the car with the blinker on and see which one isn't lit. It might be obvious: one lens is dark. Sometimes the bulb is barely glowing or looks dim compared to normal.
Common turn signal bulb sizes are 3157, 7443, 1157, and 7440. Your owner's manual has the right number for your vehicle, or read the number off the old bulb. A new one costs $3 to $8 at any auto parts store. Twist the old bulb out of the socket, push in the new one, and the fast blink stops.
If your vehicle has a third turn signal indicator (like a side repeater in the mirror or fender), check that one too. A dead repeater bulb can also trigger hyperflash on some vehicles.
Cause 2: You Just Installed LED Bulbs
If the hyperflash started right after you swapped in LED turn signal bulbs, the bulbs themselves aren't the problem. The flasher relay is working as designed. It just can't tell the difference between a healthy low-draw LED and a burned-out incandescent.
You have two ways to fix this:
Option A: Load Resistors
Load resistors wire in parallel with each LED bulb to add resistance back into the circuit. This tricks the flasher relay into seeing the load it expects. You need one resistor per LED turn signal bulb, typically a 50W 6-ohm resistor. They're sold in pairs for $8 to $15. The downside: they get hot. You need to mount them to a metal surface away from wiring and plastic.
Option B: LED-Compatible Flasher Relay
Replacing the stock flasher relay with an LED-compatible (also called a no-load or electronic) flasher relay is the cleaner fix. This relay uses a fixed blink rate instead of measuring circuit load. It blinks the same speed regardless of how much power the bulbs draw.
Finding the right LED flasher relay for your vehicle takes a little research. Look up your year, make, and model with "LED flasher relay" to find a compatible part. Some are plug-and-play replacements. Others require a minor wiring modification. Expect to pay $10 to $25.
Cause 3: Corroded Socket or Wiring Problem
If you've checked the bulbs and they're all fine, a corroded bulb socket or a loose ground connection can cause the same low-resistance reading that triggers hyperflash.
Pull the turn signal bulb out and look at the socket. Green or white corrosion on the contacts creates resistance in the wrong place and can mess with the signal the relay reads. Clean the contacts with fine sandpaper or electrical contact cleaner. Push the bulb back in firmly and test again.
A bad ground on the turn signal circuit has a similar effect. The ground wire for each light usually bolts to the body or frame nearby. Find the ground connection point for the affected light (usually under a screw or bolt behind the lens) and make sure it's tight against bare metal. Corrosion there can cause all sorts of strange light behavior, including hyperflash.
How to Diagnose It: Step by Step
- 1
Turn on the affected blinker and walk around the car
Look at every turn signal lens on that side: front, rear, and side repeater if you have one. Any lens that's not lighting up is your burned-out bulb.
- 2
If all bulbs look lit, check if you recently installed LEDs
If the answer is yes, skip straight to the load resistor or LED flasher relay fix. Your incandescent flasher relay just isn't compatible with LED bulbs.
- 3
If you haven't changed any bulbs, pull and inspect the sockets
Check for corrosion, loose contacts, or a bulb that isn't seated properly. Clean anything that looks questionable and retest.
- 4
If everything checks out, try replacing the flasher relay
A failing flasher relay can cause erratic blink rates even with good bulbs. The relay is usually in the fuse box. Check your owner's manual for the exact location. A new relay is $5 to $20.
Need a new turn signal assembly?
If the housing is cracked or the socket is burned beyond cleaning, a replacement assembly fixes it right. Find an exact fit for your vehicle.
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