Brake or tail light is not working: what are the repair options and cost?

Updated: February 14, 2021
You noticed that one of your brake or tail lights is not working. What are the repair options and costs if your car is out of warranty? Many newer cars have LED taillights, which are often replaced as an assembly. If it's just a bulb that is out, it's an inexpensive problem.
Brake light is not workingRight side brake light is out.

If you don't want to change the bulb yourself, a local dealer or auto repair shop can help. Replacing one bulb in an average car will cost $10-$55 labor plus the cost of the bulb ($1-$7). In some cars it's easy to do; in others the taillight assembly might need to be removed in order to change a bulb.

If you want to replace the bulb yourself, the key is to use the right bulb type and install it properly to avoid electrical issues. The owner's manual for your car lists the bulb types and might provide instructions on how to change one. Most auto parts stores stock common bulb types.
Bulb typeOften, the bulb type is printed on the bulb itself.
In many cars, the bulb is installed in a socket. For example, in this Honda Accord, the owner's manual says: Remove the socket by turning it one-quarter turn counterclockwise (see the photo). Pull the bulb straight out of its socket. Push the new bulb straight into the socket until it bottoms. Insert the socket back into the light assembly. Turn it clockwise to lock it in place.
To make it easier when replacing a bulb, you can also mark the position of the old bulb with a marker or snap a photo before removing it. In some cars, bulbs are installed on a board that is attached to the taillight assembly.

How long do bulbs last in a car? In some cars, bulbs can last up to 10-15 years, although in other cars, they are known to fail much earlier. It depends on where the bulb is located, the quality of the bulb and many other factors.

I've changed the bulb, why is it still not working? It's a good idea to check if the bulb is good. If the bulb is good, the next item to check is its socket. If the socket is okay, the fuse, the wirning to the bulb and the connector must be checked.

How to check if the bulb is good? In most cases, it's easy to see when a bulb is burned out.
Bad vs good bulbBad vs good bulb.
Another way to check it is to measure the resistance of the bulb using a multimeter. A good bulb should have resistance from 0 to 3 Ohms. If the multimeter shows OL, which means the resistance is out of range (no continuity), the bulb is bad. It's also possible to check the bulb using a 12V power source, or a 9V battery.

Double-filament bulbs are used for two functions; they can work,
Double-filament bulbDouble-filament bulb.
for example, as a brake light and a tail light or as a turn signal light and a tail light. Often, when one filament fails, the other might still work. When testing a double-filament bulb with a multimeter, each filament has to be tested separately.

Can a bad bulb socket cause the light not to work? Yes, when changing a bulb, the socket must be visually checked. Does it look burnt or melted?
Good and melted bulb socketThe bulb socket on the left image is melted and must be replaced.
Often the bulb doesn't work because the socket is damaged or has a bad connection; see the photo. In this case, the bulb socket will also need to be replaced. If your local parts store doesn't have it, you can order it from a dealer. A bulb socket costs from $5 to $15. In some cars, the socket comes as part of the taillight wiring harness and may cost from $15 to $35.

What can cause all taillights or all brake lights not to work? Although it's rare for two or three bulbs to fail at the same time, bulbs must be checked first.
Third brake light is not working One of the ways to check brake lights is to look at the reflection.
If the bulbs are good, it means that the electric circuit for the affected lights is down. For example, a bad brake light switch can cause the brake light circuit (and all three brake lights) not to work. If the electric circuit is down, the first step is to check the fuse.

Most cars have two or three fuse boxes; you can find the fuse location in the owner's manual. One circuit can have more than one fuse. If all the fuses are OK, the circuit must be diagnosed. In modern cars, lights are controlled by electronic control modules. Mechanics at a dealership or well-equipped auto repair shop can check any of the control modules with a scan tool or multimeter.

What to do if fuse for the affected lights is blown. A blown fuse is easy to replace, but if the fuse is blown, it means there is an electrical short. For example, one of the bulbs could be shorted or installed the wrong way. Another common problem is when wires that connect to the trailer harness rub against a metal part and short. Damaged wires inside the trunk lid harness could also short between each other and cause the fuse to blow. It's not always easy to find the reason for a blown fuse, but a knowledgeable mechanic should be able to help. Most dealers and auto repair shops charge a flat fee ($50-$130) for initial diagnostics of an electrical problem like this.