What happens when flasher relay goes out?
The flasher relay is responsible for making your turn signals blink. When it fails, you may see signals that don’t blink, blink too fast, or stop working altogether, and in modern cars, the behavior can involve the vehicle’s main control modules. In many cases, a simple relay replacement fixes the problem, but some vehicles rely on integrated systems that require professional service.
What the flasher relay does
The flasher relay feeds power to the turn signal lamps in a repeating on-off cycle, creating the blinking effect. In older cars, it’s a discrete, mechanical or electronic unit. In newer vehicles, the function may be handled by a body-control module (BCM) or a dedicated turn-signal module, which can complicate diagnosis when signaling fails.
Common symptoms when the flasher relay fails
The following signs are commonly associated with a failing flasher circuit. Note that some symptoms can also result from bulbs, wires, or grounds, so testing is essential.
- Turn signals do not blink; they may stay solid or not illuminate at all.
- Dash indicator arrows either stay lit or flicker erratically.
- Hazard lights fail to operate, or they behave inconsistently (in some cars hazards share the same relay).
- You hear no clicking sound or the cadence is abnormal when signaling.
- Hyper-flashing (very fast blinking) occurs even when all bulbs appear to be in good condition.
If you notice these symptoms, the flasher circuit or its control pathway may be failing and warrants formal testing.
Different flasher mechanisms in modern cars
Flasher systems vary by age and design. Understanding whether your car uses a traditional relay, an electronic module, or a BCM-controlled system helps guide diagnosis and repair.
Thermal/mechanical flashers
Older vehicles often use a bi-metal strip that heats and cools to make and break the circuit, producing the click-and-flash pattern. Wear or debris can cause sticking, weak flashing, or a complete failure to blink.
Electronic flashers
Electronic (solid-state) flashers rely on a timer circuit rather than heat. They’re generally more reliable but can fail if there’s a fault in the power, ground, or the unit itself.
Integrated or BCM-controlled flashers
Many modern cars do not use a separate relay. The turn-signal and hazard functions are controlled by the body-control module or a dedicated module. In these systems, a signaling failure might appear as a broader electrical fault or require software updates or module replacement.
How to diagnose the flasher relay problem
Diagnosing the issue involves ruling out bulbs, fuses, wiring, and control modules. A systematic approach helps determine whether the relay, the bulbs, or the control module is at fault.
- Check all turn-signal bulbs for burnout and replace any that are out, since a single bulb out can trigger abnormal flashing.
- Inspect the fuses for the turn-signal circuit and hazards; replace any blown fuses and verify power is reaching the fuse box.
- Inspect the wiring and grounds in the turn-signal circuit for corrosion, loose connections, or damaged insulation that could mimic a relay failure.
- Locate the flasher relay (or the turn-signal control module) and test by swapping with a known-good unit of the same type, if your car uses a discrete relay. For BCM-based systems, consult the service manual to test the module or read fault codes with a scan tool.
- Test the hazard switch and separate hazard relay (where applicable) to determine whether hazards behave normally. If hazards work but turn signals do not, the fault may lie in the turn-signal path or module.
- If external checks fail to identify a fault, consider the control module or software as a potential culprit. A dealer or qualified mechanic can perform advanced diagnostics and reprogramming if needed.
Diagnostics help determine whether the issue is a replaceable relay, faulty bulbs, wiring problems, or a control-module fault requiring professional service.
Repair and replacement options
The repair path depends on the vehicle’s design. Here are common approaches used by DIYers and professionals.
- Replace a discrete relay with an OEM or reputable aftermarket unit that matches your vehicle’s specifications.
- In BCM-based systems, the fix may involve software updates, reprogramming, or replacing the body-control module—often handled by a dealer or qualified shop.
- For older vehicles that use a universal electronic flasher, a compatible unit can be installed in place of the old relay, provided wiring and pinouts match.
- Repair any damaged wiring or poor grounds in the circuit to ensure a reliable electrical path before or after replacing the relay.
After replacement or repair, re-test the system to confirm proper operation of both turn signals and hazards.
Safety considerations and when to seek help
Faulty signaling is a safety and legal concern. If your signals are unreliable, you risk miscommunication with other drivers and potential penalties in some jurisdictions. If you’re not comfortable working with automotive electrical systems, or if the vehicle uses a BCM, consult a professional to avoid unintended electrical issues.
Summary
When the flasher relay goes out, signaling can stop blinking, blink erratically, or behave unpredictably, and hazards may be affected depending on the vehicle. Diagnostics should start with bulbs and fuses, then proceed to testing or swapping a known-good relay if the car uses a discrete unit. Many newer cars rely on the body-control module rather than a standalone relay, which may require professional software updates or module replacement. In all cases, addressing signaling issues promptly improves road safety and compliance.
What are the most common signs and symptoms of a bad relay?
Signs of relay failure include malfunctioning electrical components, flickering lights, or a vehicle that won't start. A clicking sound may also indicate a faulty relay.
How much does it cost to replace a flasher relay?
A flasher relay replacement typically costs between $60 and $120 at a professional mechanic, with the part costing around $30-$60 and the rest going to labor. DIY replacement is cheaper, with the part alone costing about $15-$60, though it can be higher depending on the part and vehicle.
This video explains how to replace the flasher relay and provides an estimate of the cost: 1mMaxTheCarGuyYouTube · Jul 17, 2024
Cost breakdown
- Parts cost: $15–$60 for the relay itself. Some high-quality or specific OEM parts may cost more, while aftermarket options can be as low as $15.
- Labor cost: Approximately $30-$60 when performed by a mechanic, but this can vary depending on your vehicle and location.
- Total cost:
- DIY: The cost of the part only, around $15–$60.
- Professional: A total of $60–$120, including parts and labor.
Factors that influence the cost
- Vehicle: The specific make and model of your car can affect the cost of the part and the complexity of the labor.
- Part quality: The price of the relay will vary depending on if it's an OEM (original equipment manufacturer) or an aftermarket part.
- Labor rates: The hourly rate charged by the mechanic in your area will influence the final price.
- Complexity: Some vehicles may require significant disassembly of the dashboard, increasing labor time and cost.
How to save money
- Do it yourself: Replacing the flasher relay is often a straightforward DIY task that can save you labor costs.
- Shop for parts: Compare prices for aftermarket or generic relays from different retailers before buying.
- Get multiple quotes: If you're having a shop do the work, get estimates from a few different mechanics to compare labor costs.
How can you tell if a turn signal switch is bad?
Symptoms of a bad turn signal switch include turn signals not responding, blinking too fast or too slow, requiring you to hold the lever for them to work, and other systems like headlights or wipers also malfunctioning. Sometimes, the switch may also have a failure in the canceling mechanism, causing the signal to continue blinking after you've straightened the steering wheel.
Common symptoms of a bad turn signal switch
- Turn signals don't work: The lights do not turn on at all when you try to use the signal.
- Intermittent operation: The signals work sometimes but not others, or only work if you hold the lever in a specific position.
- Failure to cancel: The signal continues to blink after you have straightened the steering wheel, indicating a problem with the canceling mechanism.
- Blinking speed changes: The lights might blink too quickly or too slowly.
- Hazard lights affected: Since hazard lights and turn signals often share components, a problem with the switch can also affect the hazard lights.
- Other systems malfunction: A faulty turn signal switch can sometimes cause other stalk-controlled functions to stop working, such as the headlights, high beams, or windshield wipers.
- No clicking sound: The characteristic clicking sound of the flasher relay may be absent.
What to do
- Inspect bulbs and fuses: Before assuming the switch is bad, check if a bulb is burnt out or a fuse has blown, as these are more common and simpler fixes.
- Check the flasher relay: A failing flasher relay can cause similar symptoms and is often the cause of both turn signals and hazard lights not working.
- Consult a professional: If the simple checks don't resolve the issue, a bad switch can be tricky to diagnose. It's best to consult a professional mechanic for diagnosis and repair.
What are the symptoms of a bad flasher relay?
Symptoms of a bad flasher relay include turn signals or hazard lights not working at all, flashing too fast or too slow, or staying on solid instead of blinking. Other signs can include no clicking sound, dim lights, or related electrical issues in other systems on some vehicles.
Common symptoms
- No flashing or lights: The most common sign is that the turn signals or hazard lights will not turn on at all when you use the switch.
- Flashing too fast: A rapid blinking rate often indicates a burnt-out bulb on that side, but a faulty relay can also cause this.
- Flashing too slow or erratically: An inconsistent or abnormally slow blinking can be a sign of a failing relay.
- Lights stay on solid: If the turn signal light stays on solid without blinking, it's a strong indicator that the relay has failed and is stuck in the "on" position.
Other potential symptoms
- No clicking sound: A bad relay may not produce the usual clicking sound when the turn signals are activated.
- Dim lights: The lights may appear dimmer than usual before failing completely.
- Other electrical problems: In some vehicles, a failing relay can affect other lights or electrical components, such as headlights or dashboard lights.
How to troubleshoot
- Check bulbs first: A burnt-out bulb is a very common cause of fast flashing, so it's a good first step to check your bulbs before replacing the relay, notes LiveAbout and this YouTube video.
- Consult the owner's manual: Your car's manual can help you locate the flasher relay, which can be in different places depending on the model.
- Listen for clicks: The normal clicking sound of the flasher relay is a sign that it is working. If there is no sound, or an unusual sound, it points to a problem with the relay itself or another electrical component.
- Test or replace: If the bulbs are good, the next step is to check the relay. You can often replace it with a new one to see if the problem is resolved, says LiveAbout.
