Ever tried signaling for a turn only to realize nothing’s happening? When both turn signals stop working simultaneously, it’s frustrating and potentially dangerous. Unlike when just one side fails, dual signal failure points to a system-wide issue that needs immediate attention. Let’s dive into why this happens and how you can fix it without necessarily heading to a mechanic.
What Causes Both Turn Signals to Fail?
When both your left and right turn signals fail at the same time, the problem typically stems from a shared component rather than individual bulb failures. According to research, the most common culprits include:
- Blown fuses (15-25% of cases)
- Faulty flasher relays (35-45% of cases)
- Defective turn signal switches (20-30% of cases)
- Wiring issues (10-15% of cases)
The interesting thing is that your hazard lights and turn signals often share components, which creates a useful diagnostic clue we’ll explore shortly.
Check Your Fuses First
Always start with the simplest solution: checking your fuses. This quick check could save you hours of frustration.
How to Locate and Test Turn Signal Fuses
- Find your vehicle’s fuse box (usually under the dashboard or in the engine compartment)
- Consult your owner’s manual to identify the turn signal fuse
- Remove the suspected fuse and check for a broken metal strip inside
For example, in a 2016 Volkswagen Jetta, the turn signal fuse is located in position six in the bottom row of large fuses.
You can test a fuse visually or with a multimeter set to continuity mode – a reading of 0 ohms means the fuse is good. If you find a blown fuse, replace it with one of the exact same amperage (typically 10-20A for turn signals).
A Simple Fuse Test Without Tools
If you don’t have tools handy, try this: remove the suspected fuse and swap it with another of the same amperage from a non-essential system. If the turn signals start working with the swapped fuse, you’ve confirmed a blown fuse was the issue.
The Flasher Relay: The Heart of Your Turn Signal System
If fuses check out, the next most likely culprit is your flasher relay – the component that creates the blinking effect.
Symptoms of a Bad Flasher Relay
- No blinking at all (completely dead turn signals)
- No clicking sound when signals are activated
- Turn signals that stay on without blinking
- Unusually fast or slow blinking (when all bulbs are working)
Finding and Testing Your Flasher Relay
Most flasher relays are located under the dashboard or in the fuse box. They’re typically small, cube-shaped components that you can pull out and replace.
A clever diagnostic shortcut: Many vehicles use the same relay for both turn signals and hazard lights, while others use separate relays. If your hazard lights work but turn signals don’t, the problem might be in the turn signal switch. If neither works, it’s more likely the relay.
For example, in a 2006 Toyota Corolla, the relay is located near the battery compartment, which is typical for many Japanese vehicles.
Types of Flasher Relays
| Relay Type | How They Work | Common Failure Symptoms |
|---|---|---|
| Bimetallic | Uses a heating element and metal strip | No clicking, complete failure |
| Electronic/Solid-state | Uses electronic circuits | Erratic timing, no blinking |
| Hybrid | Combines both technologies | Often fails with hazards working but signals dead |
Diagnosing a Faulty Turn Signal Switch
If both the fuses and relay check out, the turn signal switch inside your steering column might be the culprit.
Signs of a Bad Turn Signal Switch
- Turn signals work intermittently or only when applying pressure to the lever
- Turn signal doesn’t cancel after completing a turn
- Other steering column controls (wipers, high beams) fail simultaneously
- Signal works in one direction but not the other
The turn signal switch is more complex than most drivers realize. It handles multiple functions:
- Closing the electrical circuits for left/right signals
- Mechanically canceling the signals after turns
- Often integrates with wipers and high-beam controls
Advanced Diagnostics: Testing Circuits and Connections
If you’re comfortable with basic auto electrical work, you can perform more detailed diagnostics.
Using a Test Light or Multimeter
- Test for power at the bulb sockets with the turn signal activated
- Check for proper grounding
- Trace the wiring for breaks or shorts
A 12V test light can quickly help you determine if power is reaching the socket. No power at the socket but good fuses and relay? You likely have a wiring issue or switch problem.
Modern Vehicle Complications
Newer vehicles (particularly those built after 2010) often route turn signals through body control modules (BCMs) and use CAN bus technology. These systems can complicate diagnosis because:
- They may require computer diagnostic tools
- LED lighting systems often need special resistors or modules
- Multiple computers may be involved in controlling lighting functions
DIY Repair Options
Based on your diagnosis, here are your repair options:
Replacing a Fuse
- Purchase the correct amperage fuse
- Insert it firmly into the designated slot
- Test your turn signals
Always investigate why the fuse blew in the first place – there might be an underlying short circuit.
Replacing a Flasher Relay
- Purchase a compatible relay (check your vehicle manual for specifications)
- Locate the old relay and pull it straight out
- Insert the new relay in the same orientation
- Test your turn signals
For vehicles with LED lights, you may need a special LED-compatible flasher relay to prevent hyper-flashing.
Turn Signal Switch Replacement
This is more complex and often requires:
- Disabling the airbag system (follow safety procedures!)
- Removing the steering wheel
- Disassembling the switch assembly
- Installing the new switch
- Reassembling everything carefully
For most drivers, professional help is recommended for switch replacement due to safety concerns with airbags.
Comparing Repair Costs
| Component | DIY Cost | Professional Repair Cost | Difficulty Level |
|---|---|---|---|
| Fuse | $2-5 | $50-75 | Very Easy |
| Flasher Relay | $10-30 | $75-150 | Easy |
| Turn Signal Switch | $30-100 | $150-400 | Difficult |
| Wiring Repair | $5-20 | $100-300 | Moderate to Difficult |
Preventive Measures
To avoid future turn signal problems:
- Regularly check all vehicle lights during your routine maintenance
- Clean corrosion from sockets and connectors using electronic contact cleaner
- Address any unusual blinking patterns immediately before complete failure occurs
- Consider upgrading to LED bulbs with proper resistors for longer life
Understanding Turn Signal Systems Across Vehicle Types
Different vehicle manufacturers design their turn signal systems with varying levels of complexity and component locations.
American vs. Japanese vs. European Cars
- American vehicles often have turn signal relays in the fuse box under the dashboard
- Japanese vehicles frequently locate relays in the engine compartment
- European vehicles might integrate relay functions into larger control modules
For instance, BMW vehicles like the E24 exhibit unique failure patterns where hazards function but turn signals fail due to diode isolation issues.
The Relationship Between Hazard Lights and Turn Signals
The connection between your hazard lights and turn signals provides valuable diagnostic clues:
- If hazards work but turn signals don’t: Likely a turn signal switch issue
- If neither works: Probably a shared component like a relay or fuse
- If turn signals work but hazards don’t: Likely a hazard switch problem
Some vehicles, like certain Forum member’s experience with Nissans, have completely separate circuits for hazards and turn signals.
Electrical System Interdependence
Your vehicle’s turn signals don’t operate in isolation. They’re part of a complex electrical network that includes:
- The charging system (alternator and battery)
- Body control modules
- Lighting control modules
- Dashboard indicators
A weak battery or charging system problem can sometimes manifest as erratic turn signal operation.
Modern Turn Signal Technology
The latest vehicles have moved beyond simple relays and switches:
- Solid-state electronic flashers with no moving parts
- Integrated LED lighting systems
- Turn signals that communicate with stability control and lane-keeping systems
- Self-canceling mechanisms based on steering angle sensors
- Automatic hazard activation during emergency braking
These technological advances improve safety but can make diagnostics more challenging without proper tools.
Safety Implications of Faulty Turn Signals
According to the National Highway Traffic Safety Administration, properly functioning turn signals are critical for road safety. Faulty signals contribute to a significant percentage of intersection accidents.
When troubleshooting turn signal problems, remember you’re not just fixing an annoyance – you’re maintaining a critical safety system that communicates your intentions to other drivers.
Why Both Turn Signals Might Work Intermittently
If your turn signals work sometimes but not others, consider these potential causes:
- Loose connections that make contact only in certain positions
- Temperature-sensitive components (working when cold but failing when hot)
- Corrosion on relay or switch contacts
- Partial short circuits in the wiring
- Low voltage from a failing battery
These intermittent issues can be the most challenging to diagnose, often requiring systematic testing under different conditions.
With this comprehensive guide, you should be able to diagnose and potentially fix your turn signal problems. Remember that while some repairs are straightforward, others might require professional expertise – especially when dealing with airbag systems or complex computerized controls.
