The longer you own your vehicle, the more likely you are to run into electrical problems. While the problems you find will mostly consist of burnt bulbs and blown fuses, every once in a while, they can get a bit more complex.
Don’t worry! Even if you’re stressed out and worried about the costs associated with fixing the problem, the solution is usually more straightforward than you think.
Below, we take you through the most common reasons your taillights don’t work, but your brake lights do.
6 Causes of Taillights Don’t Work But Brake Lights Do
Tail lights often fail for one of the most common reasons: either due to a bad light bulb or the wrong light bulb installed in your vehicle.
Blown fuse, bad wiring, corroded sockets and plugs, or faulty control light switch, could also cause your tail lights to fail.
Although these lists are not exhaustive, they do represent the most common. Here is a more informational list of the most common reasons for failed tail lights.
#1. Bad/Wrong Bulbs.
Brake lights usually use dual filament bulbs, so when one filament breaks, only one side of the bulb works, such as the brake light but not the tail light.
Also, many manufacturers use separate bulbs for the tail lights and brake lights, so if you discover a burned out tail light, replace the bulb.
Finally, if you just replaced bulbs and are still having the same issue, the bulbs you purchased could be the wrong type of bulb. Some people say that if it fits, it must be the right bulb. This isn’t true even if it will plug in and fit. If you still have the old bulbs, look at the part number to compare it to the new replacement bulbs.
If you already threw your old bulbs away, look up your owners manual or just Google what bulb you need for your vehicle! Keep in mind, the brand doesn’t matter but the part numbers need to be cross compatible.
#2. Blown Fuses.
You may have burnt out bulbs, but it’s likely that you have a burnt out taillight fuse. To check, open your vehicle’s fuse box and check it with either a test light or a multi-meter.
If you don’t have either, then simply remove the taillight fuse and see it! Even if you can’t tell if it’s burnt out, you can swap that fuse with a different fuse with the same amp rating. If the problem shifts, then the fuse is the culprit!
When getting new fuses, always get the same amp rating! It may be tempting to increase the amp rating to ensure it doesn’t blow again, but too much amp rating can fail to protect the system from issues.
#3. Faulty Control Switch.
Home mechanics often miss this, but it’s one of the biggest reasons your taillights stop working.
The control switch in the cab of your vehicle tells your taillights when you want them on. If the switch is not working correctly, your taillights will never come on!
When this part is faulty, you will most often lose the front parking lights too.
#4. Wiring Issues/Bad Grounds.
Wiring problems can be the worst part for a lot of mechanics. Troubleshooting and finding the issue can be a pain. There will likely be wiring issues every so often.
Some common wiring issues can be: broken wires, crossed lines, or excessive corrosion, which can happen more often in older vehicles.
#5. Corroded or Damaged Sockets or Plugs.
If your car’s taillights aren’t sealed properly, everything inside your taillight assembly will be exposed to the elements.
This situation can lead to problems all over, but the most affected part is the socket itself. These will rust and corrode when they are exposed to the elements. This will cause all sorts of electrical problems.
Whenever you replace a bulb, you should check the socket itself to see if it is clean. If you see corrosion, get a wire brush and tried and true WD-40 to clean out the socket. However, if the damage is bad enough, you will need to get yourself a new socket.
#6. Bad Ambient Daylight Sensor.
Modern cars have automatic parking lights for nighttime driving, which turn off based on ambient light. Depending on where you live in the world, this might not be appropriate at night, but did you make sure it is just not too bright outside for your lights to come on?
Additionally, they can fail because of a faulty ambient light sensor or light that determines when to activate the tail lights. These are typically found even sometimes embedded in the front windshield, although it is not a common failure.
Tail Light Troubleshooting Guide
When troubleshooting, you want to KISS it. Not literally, of course, but you need to keep it simple stupid!
It’s basically Occam’s Razor form; usually the simplest answer is the problem. Before you dig into wiring harnesses and grounds, make sure the bulbs didn’t burn out and, you’re getting power!
No power usually means a blown fuse, however, it could be a faulty switch too. Those three items, bulbs, fuses, and switches, make up about 95% of the electrical problems with taillights.
Even better news is that they are also the easiest to troubleshoot and fix! However, once you exhaust those three things, you can move on to the next two. First, check power at the socket, with the known good ground first. When checking for power, make sure you have good contact with the metal terminal in the socket.
If you find corrosion or anything covering the terminal, you will need to clean it first. If you clean the terminal, try the bulb again. It could / should have been the corrosion!
If you have power (no corrosion), then it is likely a ground issue to resolve. If you do not have power, repeat these steps at the fuse. If you have power at the fuse and not at the socket, you have a wiring issue between the socket and fuse.
If you do not have power at the fuse, check for power at the switch. You guessed it, if you have power at the switch and not at the fuse, the wiring issue is located somewhere between. If you don’t have power to the switch, you have a problem somewhere between there and the battery.
Is there a fuse for the tail lights?
Yes, because almost all car models have a fuse for the tail lights, and some models even have a fuse for each side of the lights.
To find the necessary fuses, you will need to find the fuse box, which is not always easy to find. Sometimes this box will be in the trunk, under the hood, or possibly located under the dash. It is a good idea to also check your owner’s manual to see where the fuse box is located.
Can you drive with no tail lights?
No, you should not drive with no tail lights. This is dangerous and illegal in many states and countries. If you have an issue with your tail lights, you should get them fixed as soon as you can!
Not having tail lights can be dangerous, because other drivers will not be able to see your car as well and may rear end your car, or if you get pulled over, you can get a ticket for having no tail lights. So no matter how you look at it, not having the tail lights is not worth it.
Do tail lights and brake lights use the same bulb?
That all depends on the make and model of your car. In most cases, the brake lights and tail lights may use the same bulb.
However, there are vehicles that use separate bulbs for the brake lights and tail lights. If you are not sure, you might check the owner’s manual for that information.
How do you check your own tail lights?
To check you tail lights, look at the light from behind the car when the ignition is on and the headlights are on. The tail lights will be on whenever the headlights are on, and tail lights will be off whenever the headlights are off on almost every car.
Now, nothing is worse than electrical gremlins! Nothing. However, with a little automotive insight and basic electrical principles, you should be able to find out why your tail lights are not working!
Here are the most common reasons tail lights do not work, but brake lights do:
- Wrong or Bad bulbs
- Blown fuses
- Faulty light control switch
- Wiring problems or bad grounds
- Corroded or Damaged Light Sockets or Plugs
- Faulty Ambient Day Light Sensor.
It may seem like a lot at first, but most electrical problems are cheap and easy to fix, do not come back, and are not hard if you do the job right!
Even better for the novice mechanic, some of these are a problem you can literally troubleshoot and fix yourself!