Turn Signal Problems and Diagnosis

Turn Signals Not Working?

Turn signal problems and diagnoses can get confusing, especially when a system shares wires and connections with the parking, warning, and braking light systems.

Common problem sources include bulbs, wires, connectors, fuses, flasher units, and switches. So the average car owner can troubleshoot these faults with the use of a test light and, sometimes, a digital multimeter (DMM).

When dealing with any vehicle electrical circuit fault, it's a good idea to have the repair manual for the particular vehicle make and model you'll be working on. It helps you identify not only wires and components and their related connections but also how to access, troubleshoot, and replace components as necessary.

Furthermore, sometimes it is necessary to access the turn signal switch. You'll have to remove the covers and, possibly, the steering wheel. If your vehicle has airbags, it is necessary to disable the passive restraint system (airbags) before working around the switch to prevent accidentally hitting an inertia sensor that may activate the airbags.

Always follow the instructions and warnings in the repair manual for your particular model to prevent an accident. Haynes manuals are popular and practical maintenance and troubleshooting guides. Get the one for your car make and model.

To make troubleshooting easier, this guide is divided into the most common types of turn signal system failures, troubleshooting procedures, and tips to guide you toward the potential fault much faster. Just look for the section heading that describes your particular problem.

In This Article

I. One of My Turn Signals Doesn't Work: Plus, Checking a Light Bulb Socket for Ground and Power

II. One Side of the Turn Signal Lights Doesn't Work

III. My Hazard Lights Don't Work but the Turn Signals Do

IV. Turn Lights Flash Too Fast or Slow

V. Turn Signal Lights Don't Work

VI. Turn Signals Don't Flash

VII. Turn Indicators on Dash Don't Flash

VIII. Turn Indicators Don't Work But Turn Signals Do

IX. Checking the Turn Signal Switch

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X. Testing the Turn Signal Flasher

XI. Turn Lights Don't Turn Off

I. One of My Turn Signals Doesn't Work

This is one of the most common faults in turn signal systems. Here are some steps you can take to troubleshoot the problem:

1. First, check the bulb. You'll need to gain access to the bulb through the engine compartment (front light), trunk (rear light) or by removing the lens itself. Access changes depending on the model. If necessary, consult your vehicle repair manual.
2. Most likely, the turn signal bulb is a two-filament type. Make sure both filaments are in good condition, and that the bulb glass is not darkened. Otherwise, replace the bulb with another one of the same type and wattage.
3. Examine the bulb socket for corrosion or damage.
4. If necessary, check the socket ground and power connections. See the next section.

Checking a Light Bulb Socket for Ground and Power

Gain access to the light socket you need to test:

• Unplug the connector.
• Closely examine the connector, harness, housing, and socket.
• Look for signs of overheating, corrosion, and damage that may lead to a false or broken electrical connection.
• Pay special attention to ground connections.

You can use a test light here:

• After removing the bulb, clip the test light to the socket wall (ground) and touch each socket contact inside with the tip of the test light.
• Have an assistant operate the turn signal. The test light should flash—otherwise, there is something wrong with the ground or power connections.
• Connect your test light to a good chassis ground. A bolt or unpainted metal bracket will do.
• Then touch the socket contacts with your test light tip and have your assistant operate the turn lights. The test light should flash. If it does, check the ground connection at the socket.
• If the test light didn't flash, connect your test light to battery power and touch the socket wall (ground) with the tip of the test light. Your test light should illuminate. If it does, check and repair the power source connection at the socket.

You can repeat the previous test. But this time install the light bulb to the socket and back-probe the connections at the harness connector while operating the turn signal. This way you can also test the connector for a false or damaged connection.

II. One Side of the Turn Signal Lights Doesn't Work

This is a variation of the previous problems. This time, though, the left or right side of the signals doesn't work. You may see the dash indicator lamps illuminating brightly, but the turn lights won't flash.

You may be dealing with bad bulbs, a bad flasher relay, a faulty turn signal switch, or a bad wire or connector between the flasher unit and the turn signal switch.

1. First, check the bulbs to see if they are still in good shape: No darkened areas or damaged filaments.
2. Then, check the sockets for corrosion, wear, or damage.
3. Confirm the ground and power connections are working properly. Refer to the 'Checking a Light Bulb Socket for Ground and Power.'
4. Check the flasher relay. Refer to section X. Testing the Turn Signal Flasher.
5. Check the outgoing voltage from the turn signal switch to the faulty turn signal side of the circuit. Use a test light or digital multimeter.
6. If necessary, check continuity from each end of the wire, leading from the flasher relay and the turn signal switch.

You may need the repair manual for your specific vehicle make and model to identify wires and components, and possibly to gain access to them.

III. My Hazard Lights Don't Work but Turn Signals Do

The hazard or emergency lights may share the same circuit with the turn signal circuit.

1. When your hazard lights don't illuminate but the turn signals work, usually you are dealing with a faulty hazard-lights flasher.
2. However, if the flasher unit is working fine, check the fuse.
3. Also, check for a bad connection at the turn signal switch or an open in the part of the circuit that connects the flasher unit to the turn signal switch. See the section 'Checking the Turn Signal Switch.'
4. Finally, check for an electrical open or a short circuit in the wiring that connects to the external lights.

IV. Turn Lights Flash Too Fast or Slow

A change in the flashing rate of the turn signal lights isn't common but it can happen.

• If this occurred after replacing the flasher or one of the light bulbs, you may have installed the wrong type of flasher or bulb for your vehicle model.
• Or one of your light bulbs may have burned out. A burned-out bulb can cause the indicator light to flash faster.

Other potential problems that may lead to a change in the flashing rate:

• Poor ground or power connection at the lamps.
• A loose connection at the turn signal switch.
• If the lights are flashing faster than normal, make sure the alternator is not overcharging the battery.
• If the lights are flashing slower than normal, the alternator may have an undercharge condition, or your battery may be undercharged.

V. Turn Signal Lights Don't Work

Another common problem occurs when none of the turn signal lights work.

Note: Normally, you are dealing with a blown fuse, a bad flasher unit, or a faulty turn signal switch. Locate the fuse using your car owner's manual or vehicle repair manual, or check the 'Checking a Light Bulb Socket for Ground and Power' section above, or the 'Testing the Turn Signal Flasher' further down.

Other circuit problems may also lead to this condition:

1. Check the condition of the bulbs.
2. Make a visual inspection of the bulb sockets—look for corrosion and damage.
3. Verify that the ground connection is working properly. See the section 'Checking a Light Bulb Socket for Ground and Power.'
4. Also, check for an open (most likely) or a short.

VI. Turn Signals Don't Flash

If the emergency lights and turn signal lights illuminate but don't flash, check first for a burned-out bulb. This is the most common cause. If not, you may be dealing with a bad flasher unit or a bad turn signal switch. See the sections 'Testing the Turn Signal Flasher' and 'Checking the Turn Signal Switch.'

If necessary, make the following circuit checks:

Check for a blown circuit fuse.

1. Verify that circuit connections are not loose, corroded, or unplugged.
2. Inspect the wiring harness or terminals for the rear section of the circuit.
3. Check for a bad connection between the turn signal switch and the flasher or between the flasher and the ignition switch.
4. Check the power side connection to the turn signal switch for a bad contact or open.
5. Finally, check for an open or short in the lamp's circuit.

VII. Turn Indicators on Dash Don't Flash

You may know there's something wrong with your turn signal lights because the indicator lights on the instrument panel illuminate but don't flash as usual.

1. First, check that your turn lights work properly. If they come on but don't flash, most likely the flasher unit is bad.
2. If one of the signal lights doesn't come on, check the bulb; check the bulb socket for corrosion or damage; check for a bad ground at the socket. See the 'Checking a Light Bulb Socket for Ground and Power.'
3. Check for an open in the circuit, between the light(s) that doesn't work and the turn signal switch.

VIII. Turn Indicators Don't Work but Turn Signals Do

Another problem you may encounter is that your indicator lights don't work at all, but the outside turn lights work fine. Possible causes:

• Blown-out indicator bulbs
• Corroded bulb sockets
• A bad ground
• A problem with the flasher unit

If necessary, consult your vehicle repair manual to gain access to the bulbs on the instrument panel and ground connection.

Although some models use a separate light for the left and right turn indicators, other models use a single light for both turns.

• If your instrument panel has only one indicator light for both left and right, check the flasher unit. Some vehicle models combine the brake light, taillight, and turn signal into one light bulb.
• If you have replaced one of the lamps, make sure the bulb is installed properly.
• If the two separate instrument panel indicator lights don't work but the outside turn signal lamps work, check the indicator light bulbs and flasher unit.

IX. Checking the Turn Signal Switch

Troubleshooting the turn signal switch is pretty much straightforward. Usually, depending on your particular model, getting access to the switch electrical connector is the hardest part.

For this test, it is a good idea to consult the vehicle repair manual for your particular model. You need to identify wires and the best way to access the signal switch electrical connector. Also, if your model has airbags, you may need to disable the system to prevent the bags from accidentally inflating. If necessary, your manual will walk you through the process for your particular model.

1. Find the wiring diagram for the turn signals in your vehicle model using the repair manual.
2. Identify the wires carrying power from the flasher unit to the switch and the wires carrying power from the switch to the turn signal lights. Check the color designation for these wires and, if necessary, the terminal number on the electrical connector of the turn signal switch.
3. Gain access to the turn signal switch electrical connector. You may need to remove an under-dash panel or column cover to see the electrical connector.
4. Look for the wires that you identified in Step 2.
5. Turn the ignition key to the On position, but do not start the engine.
6. On the switch connector, find the wire that supplies power to the turn signal switch.
7. Connect your test light to a good ground under the dashboard - a metal bracket or bolt will offer a good ground.
8. Operate the switch to turn the left turn signal light.
9. Back probe the wire that supplies power to the switch; the test light should flash. If the test light doesn't flash, there is a problem with the flasher unit or an open or short between the switch and the battery power source.
10. Back probe the wire at the connector that supplies power to the left turn signal lights; the test light should flash. If the test light doesn't flash, the switch is bad. Replace the switch.
11. Back probe the wire that supplies power to the right turn signal lights; the test light should not light. If the test light illuminates, replace the switch.
12. Repeat the test, but this time operate the switch so the right turn signals light. The only difference in your results this time is that your test light should flash when back probing the terminal that supplies power to the right turn signal lights, but not the left turn signal lights. Otherwise, you need to replace the switch.

X. Testing the Turn Signal Flasher

NOTE: This guide deals with analog-type flashers. If your system is equipped with a solid-state unit, consult your vehicle repair manual for special instructions. Also, make sure to use a digital multimeter with at least 10 Mega-ohm of impedance to protect sensitive circuits in your vehicle as you troubleshoot electrical systems.

A good way to test the flasher unit is to use a known good unit, but that may not be practical. So the next best choice is to test the suspected flasher while installed in the vehicle. Your circuit connections may differ from the outline described here, but you'll find the next general steps helpful. If necessary, consult your repair manual.

1. First, locate the flasher; you may find the unit under the dashboard near the steering column, or near the battery in a junction box or 'power center.' Consult your vehicle repair manual, if necessary.
2. Locate the wiring diagram for the turn lamps in your vehicle repair manual.
3. Identify the colors of the wires that connect to the flasher unit. Identify the wire that supplies power to the flasher, and the wire going from the flasher to the turn signal switch to operate the turn signal lamps.
4. Connect your test light to the ground.
5. Turn the ignition switch to the On position but do not start the engine.
6. Operate the turn signal switch in either direction (left or right).
7. Back probe the power wire that connects to the flasher unit. The test light should illuminate. Otherwise, you have a blown fuse, or there's an open between the flasher unit and its power source (fuse box or battery).
8. Without operating the turn signal switch, back probe the wire going from the flasher unit to the turn signal switch. The test light shouldn't flash. Otherwise, the flasher is no good.
9. Now, operate the turn signal switch and back probe the wire going from the flasher unit to the turn signal switch. The test light should flash. Otherwise, the flasher is no good.

The next video shows you a common procedure when replacing a flasher unit on a GMC truck. Depending on your particular vehicle's make and model, you may or not need to remove the dashboard trim. On some models, the flasher is readily accessible. Consult your vehicle repair manual.

XI. Turn Lights Don't Turn Off

This is a special turn signal failure. It has to do with the mechanical operation of the signal switch rather than an electrical system failure. For example, you signal traffic with your intention to turn left or right, but after cornering, the turn signal continues to flash.

There are two reasons for this type of failure: Either the canceling finger inside the switch is broken, in which case you need to replace the switch; or the canceling cam/clockspring is broken, in which case you need to replace the cam or assembly, depending on your particular model.

In most cases, the repair is within the reach of the average car owner. Still, consult the repair manual for your particular vehicle make and model, especially if your model has airbags. You'll need to disable the system for safety reasons. Also, your repair manual will tell you what specific tools you need, if any, and the procedure to follow.

Always Check All Lights

Turn signals, and the system they are part of, can fail in many ways. When facing a problem, always check every light so that you know what part of the system or lights is failing. This will make troubleshooting, and fixing the problem, easier and faster. This guide is designed to help you make your repair faster and get back on the road safely.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: I have a 2004 Mazda 6. Left side turn indicators sometimes work and sometimes don't, both inside and outside. The other side indicators work just fine. When using the alarms, I have the same problem with the left side indicators inside and outside. What do you think is the problem?

Answer: Seems like you got a loose ground or power wire in the circuit. Check the sockets on that side of the circuit. Also, check the switch-harness outgoing voltage for that side of the circuit. You can use a test light or voltmeter. You may need the wiring diagram in your repair manual to id the wires.

Question: I have a 2014 model, 3.2 4x4 Ford Ranger. The front and rear, right turn signals don’t work but the light indicator on the dashboard work. Any advice?

Answer: There could be a problem with the turn signal switch or a faulty connection. Use the repair manual for your model to locate, gain access to the switch and connectors, if necessary. If you don't have the manual, check the reference section of your local public library. They may have a copy for your specific model.

Question: Yesterday, I bought new turn signal bulbs for the left rear and right rear of my vehicle. My left rear already burned out. Why would it burn out the next day?

Answer: Make sure the proper fuse is used to protect the circuit - and check for loose wires around the socket and check the socket itself.

Question: My turn signal on the left stays on in the head and tail light when the car is off. Also, it doesn't flash when I signal to the left. What could be the problem?

Answer: Probably the issue is with the switch or control module, depending on your particular model. The component is mounted on the steering column or next to it. You may need the vehicle repair manual for your particular model is you want to test it or replace it yourself.

Question: My turn signals work but flash twice the speed. On the outside, only the rear indicator light does not illuminate. I've checked the bulb and fuse but no luck. What could be wrong?

Answer: Check the ground and power connections at the non-working light. There could be a loose or broken wire. Check the socket with a testlight.

Question: How can I tell if my multiswitch is bad?

Answer: The most common fault in the multifunction switch is wear of the turn signal contacts. They wear out and may begin to fail intermittently or not turn the signal, signal may not cancel; you may experience similar problems with the wipers and headlights. Other than that, you need to gain access to the switch and operate the switch while testing incoming and outgoing voltage with a test light as you operate the different settings. You may need your vehicle repair manual to check the wiring diagram for your particular model.

Question: My front and rear signals work on my 2006 GMC Yukon XL Denali, but the right side of the vehicle does not work. The hazard work the same way driver front and rear and the right do not work when the switch is turned on. I changed the flasher and the problem remains. What could be the cause of this problem?

Answer: Make sure the light bulbs and socket are good on that side of the circuit. Use a test light to make sure you have good grounds and power, reaching the sockets. Fix as necessary. Otherwise, check the signal switch connections for that part of the circuit using the test light.

Question: My left turn signal was blinking quickly, and my rear light was out. Now when I flick the left signal, the right one blinks. And when I activate the right one, nothing happens at all. What could be the problem?

Answer: Usually, this is caused by a bad ground. Check the wiring diagram for your particular model and use a test light to test for faulty grounds in the circuit. If you don't have the repair manual, try the reference section of your local library.

Question: 2017 Toyota Harrier indicator light are working, but why my hazard lights are not working?

Answer: The flasher for the hazard lights might have failed. Your turn lights should work.

Question: All my left-hand side indicators and hazard warning work; however, the right side doesn't. Would breakdown assist and would it be covered, as it's unsafe to drive home? And as far as I can make out it’s not the bulbs or fuses in the car. Although I haven't checked fuses or relays in the engine. Also, the side repeater in the driver's door, which is a fixed unit, that bulb is blown, would it take the whole right side out?

Answer: Usually, this is due to a faulty turn signal switch. But you might want to check the bulbs first, and any potential faulty signs you may see in the sockets or wiring to them. Try swapping the door light bulb with the opposite one and see what it does. You can also test the switch using a test light. Go over section two in the post.