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A Comprehensive Guide On Turn Signal Relay

A Comprehensive Guide On Turn Signal Relay

Turn signal relay, or what is also known as turn signal hazard flasher, is the electrical apparatus that controls the turn signal. Most turn signal lights on cars are controlled by a flasher, which is also referred to as a relay. It is the part that allows the lights to flash on and off. This is made possible by routing the power to the turn signals via a flasher or relay that sends pulses of power to the lights rather than a steady stream. Upon completing your turn and turning the steering wheel back to center, a cam on the steering column catches on the turn signal lever, cancelling the operation of the turn signal. 

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Relays come in different shapes, designs and sizes which depend on the particular needs of the car. Among all systems in the car, it is the easiest to analyze and solve when it goes bad. It will be difficult to maneuver or turn your car around safely with a bad signal flasher. The good thing is, it is easy to troubleshoot a failing turn signal relay. 

How do I know if my turn signal relay is bad?

Typically, a turn signal relay issue is mainly due to a burned bulb or a malfunctioning turn signal relay. An issue with a bad turn signal relay shows many symptoms. This is why a driver will easily notice if there is a potential issue, here are some common symptoms of a failing turn signal system:


Non-functioning Turn Signal Relay


The most common sign that you have a bad turn signal relay is a broken flasher. This causes the lights to stop working when you push the hazard light button. While a non-functioning turn signal relay does not result in serious engine performance problems, it should still be addressed right away because driving with turn signals not working is very dangerous.


A signal blinking really fast may mean a dead bulb. A turn signal bulb like any broken bulbs can be easily replaced and it is not expensive. This problem is ain’t that bad. 


However, if the bulbs are not the culprit, you have to replace the turn signal flasher for good. Make sure you check flasher relays for hazard lights or turn signals before replacing the turn signal relay since they are separated in some vehicles.


One side of the Turn Signal Lights is Not Functioning


This is a variation of the previously mentioned problems. In this case, however, the left or right side of the signals is not functioning. This time, the dash indicator lamps are lighting on brightly, but turn lights aren’t blinking. You may have an issue with a faulty turn signal switch, a bad flasher relay, bad bulbs, a bad wire or connector between the turn signal switch and the flasher unit. What you can do:


  1. Inspect the bulbs to check if they are still in good shape: No damaged filaments or darkened areas.
  2. Check for damage, corrosion or wear on the sockets.
  3. Check if the ground and power connections are functioning properly. 

How to Check A Light Bulb Socket for Ground and Power

           Access the light socket that needs to be tested and use a test light:

  • Unplug connector.
  • Closely inspect the harness, connector, housing and socket.
  • Check for signs of damage, corrosion and overheating that may result in a false or faulty electrical connection.
  • Look for ground connections.
  • After taking off the bulb, clip the test light to the socket wall (ground) and with the tip of the test light, touch each socket contact inside. 
  • Have someone else operate the turn signal. When the test light is flashing, it means there is nothing wrong with the ground or power connections. If not, then there is a problem with the ground/power connections. 
  1. Check the relay. Here’s how you can test your turn signal flasher:
  • Locate the flasher. It may be positioned under the dashboard near the steering column or near the battery in a junction box. If needed, see your vehicle repair manual.
  • Find the wiring diagram for the turn lamps in the manual.
  • Identify the colors of the wires connecting to the flasher unit. Find out which wire supplies power to the flasher, and which wire is going from the flasher to the turn signal switch to control the turn signal lamps.
  • Connect the test light to ground.
  • Turn the ignition switch on, but don’t start the engine.
  • Operate the turn signal switch in either left or right direction.
  • Back-probe the power wire connecting to the flasher unit. The test light should turn on. Otherwise, there is a blown fuse, or an open between the fuse box or battery and the flasher unit.
  • Back-probe the wire going from the flasher unit to the turn signal switch, but do not operate the turn signal switch. The test light should not flash because if it does, it means the flasher is faulty.
  • This time, back-probe the wire going from the flasher to the turn signal switch while operating the turn signal switch. The test light should flash because if it is not, it means the flasher is bad. 

Note: This guide is for analog type flashers. If your system has a solid state unit, see your vehicle repair manual for special instructions.

  1. With a digital multimeter or a test light, check the outgoing voltage from the turn signal switch to the faulty turn signal side of the circuit. 
  2. If needed, inspect the continuity from each end of the wire, leading from the relay and the turn signal switch.


A repair manual for your specific car make and model might be needed for you to identify wires and parts, and to gain access to them.


Turn Signal Relay Keeps Lighting


Another indication that your turn signal relay is faulty is that it stays on when it should be flashing. Even if it’s illuminating, those behind you or in front of you will not know if you want to turn left or right, or what direction you are going. It will not also serve its purpose during emergency situations. Usually, the cause is an electrical issue. For this problem, you would need to have it checked by a professional. 


Other Lights Are Not Functioning


In some cases, other lights like the brake lights, headlights or running lights are not working along with your turn signal relay. This is because in some vehicles other lights are wired through or with the flashes so they also get affected when the flasher fails. 


Although problems with the turn signal relay will usually not affect the driveability or operation of your car, they can lead to problems that can compromise the visibility and safety of your vehicle. They are not as complex as other parts in your vehicle but there are cases that it can be difficult to detect because of the complicated nature of electrical systems. So if you begin to suspect that your car’s turn signal relay is having issues, have your car checked by a professional mechanic to determine if the relay needs to be replaced.


How do you change a turn signal relay?

As mentioned earlier, troubleshooting your turn signal relay is not difficult. As a review, turn signals go bad when it does any of these things: coming on without flashing, flashing rapidly, or not turning on at all. If your turn signal doesn’t come on or flash, you’ll need to replace it. Here is how you can replace your turn signal relay:


First, purchase a new turning signal switch. Second, find your relay cluster location. Most car owner’s manuals that come with your car will indicate where the location is. Next, remove the old turn signal relay and replace it with the new one. It’s very easy to install so you won’t have to be worried about not properly installing it. Once you’re done, you’re good to go. Your turn signal relay will start flashing and you’re back to driving safely on the road.


What To Do When Further Troubleshooting is Needed


If replacing the turn signal relay still does not solve the problem and you are sure that the turn signal bulbs are working, the problem might be something more serious and it may require electrical troubleshooting. If you are not adept in electrical stuff, this can be a little frustrating as you will have to track down a loose wire or a ground that is not grounding. You can do the following:


  1. Check the connections. You need to access the back of the turn signal housings so you can replace the bulbs. You can also find here the plugs connecting the tail lights and front turn signals to the electrical system of the car. Unplug them and plug them back one at a time. If you’re lucky, the act of unplugging and replugging can solve the issue and restore the connection. Do not be surprised if the culprit is one of the plugs you least likely thought to affect the turn signal system since turn signals are tricky.
  2. Look for bad grounds. A bad ground connection is most likely the cause when your turn signal fails to light up or doesn’t blink. In most cars, you will know the wires are ground when they are either brown or black. In any case, trace the suspected ground wire from the bulb housing to its termination point (the point at which it screws to the chassis). Once you find this, loosen and retighten the ground connection. To be sure, you can take it off and clean everything with the use of a steel wool.
  3. Check random fuses. This may sound absurd but due to the trickiness of turn signal systems, there are all sorts of inexplicable solutions for them. It’s a good idea to check all fuses when changing a turn signal or solving other unexplained electrical issues. A bad circuit that may seem unlikely to be the reason since it has nothing to do with brake lights or turn signals can somehow be a culprit to its demise. 

How much does it cost to replace a turn signal relay?


The cost of replacing a turn signal relay can range between $91 and $229. It depends on the type of vehicle you are driving and the auto repair shop where you have your vehicle serviced.

Where is the turn signal relay located?


It’s located at the driver’s end. You can find it amidst the doors and the dash. If not, it can be placed against the wheel, under the dash. It is likely covered with a door labeled “fuse”, or you can see images of the fuses and its functionality printed over.


Turn Signal Relays Replacement Solutions


There are a few courses of action you can do to replace your faulty turn signal relay. One course of action is to replace the turn signal relay part on your own as mentioned earlier. But if you choose this option, make sure you are knowledgeable enough about this kind of replacement and confident in your abilities. It is also a must to have the exact same part that is currently in your vehicle. This is important as only the putting the correct part will ensure that it will work properly in your car. 


If in doubt with your knowledge and abilities, better take your vehicle in to a professional mechanic. You can depend on them to determine the exact cause of the problem and give you a price estimate. A mechanic will know the method of replacing your turn signal relay so no need to fuss about reading your car’s owner manual. No need to take anything apart on your own, the mechanic will repair everything for you. It may be costlier but it is the better move if you are not confident enough to replace your turn signal relay on your own. 




Once you start noticing that there is an issue with your turn signal relay, you should get it fixed as soon as you can. This may not directly affect the mechanical operation of your car but it can still lead to serious car accidents that can endanger you, your passengers and those around you on the road. A turn signal relay that is not functioning as it should be will not serve its purpose. When it is functioning properly, signal lights flash in a rhythmic pattern to catch the attention of other drivers and let them know your intention. This is very important to ensure your safety, your passengers’ safety and other motorists’s safety as well. 




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