Why wont my tail lights turn on?
Tail lights failing to illuminate are usually caused by a few common issues, such as a blown fuse, a burned-out bulb, or a bad ground or wiring connection. Many problems are fixable with basic checks.
In this article, we explain the typical causes, how to diagnose them safely, and practical steps to restore tail-light function. We cover both traditional bulb-based systems and modern LED/Can-bus setups, plus guidance on when professional help is advisable.
Common causes for tail light failure
These are the most frequent culprits, typically encountered in passenger cars, trucks, and SUVs. Start with the simplest checks before moving to more complex diagnostics.
- Blown fuse for the tail-light circuit (check the vehicle’s fuse box and replace with the same rating).
- Burned-out tail light or brake light bulbs (filament burn or LED failure).
- Faulty or corroded bulb sockets or wiring that prevents proper contact.
- Inadequate ground connection at the tail light housing (poor grounding can stop current flow).
- Faulty brake light switch or wiring that fails to activate taillights when braking.
- Damaged or pinched wiring harness or a loose connector in the tail-light circuit.
- Relay or control module issues (in newer vehicles with CAN bus or body control modules).
- Moisture or condensation inside the tail light assembly causing short or corrosion.
Conclusion: If you find one of these issues, replace fuses or bulbs, clean contacts, reseat connectors, or fix grounding as needed to restore operation. Moisture should be dried and sealed to prevent recurrence.
Modern vehicle considerations
On newer vehicles, tail-light circuits can be managed by a body control module or CAN-bus system. When these systems fail or register a fault, you may see non-specific lighting symptoms or warning messages. In such cases, diagnostic tools or dealer-level servicing may be required.
How to diagnose tail light problems: a step-by-step approach
For a systematic check, follow these steps from simplest to most involved. Use basic safety precautions and, when in doubt, consult a professional.
- Verify power and ground at the tail light socket using a test light or multimeter with the vehicle lights on. If there’s no power, focus on fuses, relays, and switches.
- Inspect fuses and relays: locate the tail-light fuse(s) in the fuse box, replace any blown fuses, and test the relay if equipped.
- Remove and inspect the tail light bulbs (or LED modules): check filaments or individual LED units; replace any burnt-out bulbs or faulty LEDs.
- Inspect the bulb sockets and wiring for corrosion, cracks, or loose contacts. Clean or replace as necessary; reseat connectors firmly.
- Check the grounding: ensure the tail light housing ground screw/strap contacts bare metal, and verify continuity to chassis ground.
- Test the brake light switch (if applicable): with the brake applied, check whether the tail light and brake light circuits are activated; adjust or replace the switch if needed.
- Inspect for moisture or condensation in the tail light enclosure and reseal if necessary; dry the area thoroughly and reseal to prevent recurrence.
- If power and grounds are present at the bulb socket but the lights don’t illuminate, the issue may be a control module or CAN-bus fault; consult a professional and consider using an OBD scanner with lighting data.
Conclusion: A careful, methodical check typically reveals the exact failure point, from a simple bulb to a faulty module. If you identify a complex fault, avoid ad-hoc fixes that could cause more damage.
Safety and when to call a professional
Working with vehicle electrical systems carries risk, including battery shock, short circuits, and potential legal implications if taillights are out while driving. If you’re unsure about any step or the fault appears to involve the vehicle’s computer, lighting control module, or adjacent circuits, seek professional service.
Summary
Tail lights failing is commonly caused by a blown fuse or bulb, bad ground, or wiring/connectors issues. A systematic approach—check fuses and bulbs, inspect sockets and grounds, test the brake switch, and verify power at the socket—usually solves the problem. For modern vehicles with CAN-bus and body control modules, a persistent fault might require diagnostic tools or professional help. Regular maintenance, including checking for moisture and ensuring secure connections, helps prevent tail-light failures and keeps your vehicle street-legal and safe.
How to tell if a tail light fuse is blown?
Use a test light to see if the current is passing through the fuse. If not, the fuse is blown and needs to be replaced. Change the fuse immediately and check the tail lights again. If the issue still persists, the problem is not with the fuse.
Why won't my tail lights turn on?
Your tail lights won't turn on due to a blown fuse, burnt-out bulbs, a faulty bulb socket, or problems with the wiring or light switch. Start by checking and replacing the fuse for the tail lights, then inspect the bulbs for burnout, and finally, examine the sockets and wiring for any corrosion or damage.
This video explains the common reasons why tail lights might not be working: 1mVehicle FreakYouTube · Aug 20, 2023
Common causes and solutions
- Blown fuse: This is a very common cause. Find the fuse box in your vehicle's manual, locate the tail light fuse, and replace it if the metal wire inside is broken or melted.
- Burnt-out bulbs: Both tail light bulbs could be burnt out at the same time, but it's more likely there's a separate problem if this is the only issue. Visually inspect the bulbs and replace any that are burnt out.
- Faulty socket or wiring:
- Socket: Check the bulb socket for corrosion, bent pins, or other damage, especially if moisture has gotten inside the light.
- Wiring: Inspect the wiring harness for any signs of damage, such as being frayed, disconnected, or broken. This is common near the tail lights where moisture can enter.
- Faulty headlight switch: A problem with the headlight switch itself can also prevent the tail lights from turning on.
This video shows how to diagnose tail light problems: 1mVehicle FreakYouTube · Aug 20, 2023
When to seek professional help
- If you have checked the fuses and bulbs and the problem persists, or if you are uncomfortable with electrical troubleshooting, take your vehicle to a qualified mechanic.
- A professional can use a multimeter to test for voltage at the bulb socket or use a scan tool to check for diagnostic trouble codes related to the lighting system.
What could be the cause of the tail light of your vehicle is not working?
If you have a malfunctioning tail light, it could be a matter of a blown fuse. The fuses work with your car's electrical panel and if they're blown, it can cause several lights to stop working. Replace the fuse and see if this helps. Another issue may be related to your wiring.
Will AutoZone fix my tail light?
No, AutoZone does not typically provide professional repair services to fix a tail light, but employees may offer guidance or a quick hand with a simple bulb replacement if they are not busy. They do sell the necessary parts, such as bulbs, lenses, and repair kits, which are intended for DIY installation. You can also buy a bulb from them and ask for assistance, as many customers report receiving help with simple fixes like this, say Reddit users.
What AutoZone can do
- Sell you the parts: They have tail light bulbs, complete tail light assemblies, and lens repair kits with tapes and films for minor crack repairs.
- Provide guidance: Employees can help you identify the correct part and offer advice on how to replace it yourself.
- Assist with simple jobs: Depending on the store's policy and how busy they are, an employee may be willing to help you with a quick bulb replacement or demonstrate the process.
What AutoZone does not do
- Perform repairs: They do not offer a full-service repair for your tail light.
- Install complex parts: They are generally not equipped to handle more complex issues like wiring problems or replacing a full tail light assembly.
