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How Can You Troubleshoot Common Issues with Taillights?
Taillights are critical for road safety—they let other drivers see your car from behind, signal stops, and indicate turns. When they fail, it puts you at risk of accidents and can even get you a ticket. The good news is that most taillight issues are easy to fix with basic tools and a little know-how. Let’s break down how to troubleshoot common problems with taillights, step by step.
1. Check for a Burned-Out Bulb
The most common reason taillights stop working is a burned-out bulb. This is simple to diagnose and fix.
- How to tell: If one taillight is off but the other works, or if the brake light works but the regular taillight doesn’t, a burned-out bulb is likely the culprit. For example, if your left taillight is dark but the right one glows, the left bulb is probably dead.
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What to do:
- Turn off the car and open the trunk (or access panel inside the car, near the taillight).
- Remove the taillight cover—this usually involves unscrewing a few bolts or popping clips (check your car’s manual for exact steps).
- Pull out the bulb socket gently. The bulb should twist or pull out of the socket.
- Look for a blackened or broken filament (the thin wire inside the bulb). If it’s damaged, the bulb is burned out.
- Replace it with a new bulb of the same type (check the old bulb for the part number, like 1157 or 7440). Push or twist it into place, then test the taillight by turning on the car’s lights.
Burned-out bulbs are cheap (usually $5–$15) and take 10–15 minutes to replace. Always replace both taillight bulbs at the same time if they’re old—this prevents one from failing soon after the other.
2. Inspect for a Faulty Fuse
If both taillights stop working at once, the issue might be a blown fuse. Fuses protect the electrical system from damage, and a surge can cause them to “blow” (break), cutting power to the taillights.
- How to tell: If all taillights (including brake lights and turn signals) are off, or if only the taillights fail while other lights (like headlights) work, check the fuse. Your car’s manual will show where the fuse box is (usually under the dashboard or in the engine bay) and which fuse controls the taillights (labeled “taillights,” “tail,” or “stop/tail”).
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What to do:
- Locate the fuse box and open the cover. Use the diagram on the cover to find the taillight fuse.
- Pull out the fuse with a fuse puller (often included in the box) or a pair of needle-nose pliers.
- Check the fuse: a good fuse has a solid metal strip inside; a blown fuse has a broken strip or black marks.
- Replace the blown fuse with a new one of the same amperage (written on the fuse, like 10A or 15A). Never use a higher-amperage fuse—it can damage the wiring.
- Test the taillights. If they work, you’re done. If the new fuse blows again, there’s a short circuit (see step 4).
Fuses are inexpensive ($2–$5) and easy to replace, making this a quick first check for total taillight failure.
3. Test the Brake Light Switch
Brake lights are part of the taillight system, and a common issue is brake lights not turning on when you press the pedal. This is often caused by a faulty brake light switch.
- How to tell: If your regular taillights work, but the brake lights don’t (or only one works), the switch is likely the problem. The switch is usually located under the brake pedal—when you press the pedal, it activates the switch, which sends power to the brake lights.
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What to do:
- Find the brake light switch: it’s a small plastic or metal piece attached to the brake pedal arm.
- Check for loose connections: unplug the switch’s electrical connector, then plug it back in firmly. Sometimes a loose plug causes the issue.
- Test the switch: have a helper press the brake pedal while you check if the switch moves. If it’s stuck or doesn’t move, it needs to be replaced.
- Replace the switch: buy a new switch (matching your car’s make and model, $10–$30), unplug the old one, and screw or clip the new one into place. Test the brake lights—they should now work when the pedal is pressed.
This fix takes 20–30 minutes and requires no special tools, just a screwdriver in some cases.
4. Look for Wiring Problems
If bulbs and fuses are fine, the issue might be with the wiring. Over time, wires can fray, corrode, or come loose, cutting power to the taillights.
- How to tell: Flickering taillights, lights that work intermittently, or one light that works sometimes and not others often point to wiring issues. Moisture, rodents, or wear from opening/closing the trunk can damage wires.
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What to do:
- Inspect the wiring harness: follow the wires from the taillight assembly to the car’s main wiring. Look for frayed insulation, exposed wires, or corrosion (green/white buildup).
- Check connections: the taillight assembly connects to the wiring with a plastic plug. Unplug it, check for dirt or corrosion, and clean it with a dry cloth or electrical contact cleaner.
- Fix loose or broken wires: if a wire is loose, reconnect it. If it’s frayed, strip off a small piece of insulation (1/4 inch), twist the exposed ends together, and cover with electrical tape or a wire connector. For corroded wires, cut out the bad part and splice the good ends together.
- Test the taillights: after fixing the wiring, turn on the lights to see if they work.
If wiring damage is severe (e.g., chewed by rodents), you might need to replace the entire wiring harness, but this is rare. Most wiring issues are easy to spot and fix.
5. Check for a Faulty Taillight Assembly
In newer cars, taillights are often part of a single assembly (a plastic housing with bulbs or LED panels). If the assembly is cracked or damaged, it can cause lights to fail.
- How to tell: If the taillight lens is cracked, moisture can get inside, damaging bulbs or wiring. LED assemblies might have a burnt-out circuit board, causing the entire light to fail.
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What to do:
- Remove the taillight assembly (screws or clips hold it in place, as with bulb replacement).
- Check for cracks, moisture, or damage: if water is inside, dry it out and seal small cracks with silicone caulk. For large cracks, replace the assembly.
- Test LED assemblies: if LEDs don’t work, the circuit board might be faulty. Replace the entire assembly (cost varies, $50–$200) as LED boards are hard to repair.
This is a last-resort fix, but assemblies are designed to be replaced easily, with steps in your car’s manual.
FAQ
Why do my taillights work but my brake lights don’t?
This is usually a bad brake light switch (under the brake pedal) or a broken wire to the brake lights. Check the switch first—it’s the most common cause.
Can I drive with a broken taillight?
No, it’s unsafe and illegal in most places. Other drivers can’t see you stopping or turning, increasing crash risk. Fix it as soon as possible.
How often should I check my taillights?
Check them monthly: turn on the lights, have someone stand behind the car, and test brakes, turn signals, and regular taillights. It takes 2 minutes and prevents issues.
Why do my taillights keep burning out?
Overheating from a loose bulb (vibration damages the filament) or a bad socket (corroded or loose) is often the cause. Clean the socket with sandpaper and ensure bulbs are tight.
Are LED taillights harder to troubleshoot?
They’re similar—check fuses and wiring first. If LEDs fail, the entire assembly usually needs replacement, but they last longer than traditional bulbs (50,000+ hours vs. 1,000 hours).