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If your tail lights are not working, there are a few causes behind it with the most popular being – your light bulb went out! Taillights use a dual filament bulb (in many cases) and even if your brake light is working, the tail light filament in the light bulb could be broken.

It could be frustrating to figure out what is going on in this case, since everything looks like it’s working, but really only one part of it works (the brake light). If you have different light bulbs for brake light and tail light, then the problem with a light bulb is a bit more obvious.

Besides the light bulb burning out, the problem with tail lights not working could also include a blown fuse on the tail light circuit, the corroded socket of the light bulb, and bad wiring. You could have a short circuit, this is why the first thing you may want to check in this case is a blown fuse. 

Of course, changing a fuse will not solve your problem completely, since you still need to know what has caused this excess current. Electrical problems in your car are NOT DIY projects! Please seek help from a specialist.

Problems with not working tail light usually come down to the following:

  1. Fuse is blown
  2. Bulb went out
  3. Light socket dirty, broken, or corroded
  4. Bad wiring
  5. Bad ground
  6. Faulty control switch
  7. Ambient daylight sensor problem
  8. Wrong bulb (if just installed)

Now, let’s look at them on the individual level:

#1. Your fuse is blown

Even though a blown fuse may not be your problem, it is one of the easiest things to check for and it should be done first. The purpose of the fuse is to break the circuit when overcurrent is detected (any amount over the size of the fuse).

Its whole purpose is to keep your electrical devices from getting damaged. Very often light bulbs in a car run on their own isolated circuit and there is one fuse that protects it.

This basically means that even if your Tail light bulb is double filament (brake light and taillights each have separate filament in one lightbulb), they will be on two different circuits with two different fuses.

Here are some basic steps for changing your fuse in a car:

  • Step 1. Find a fuse box in your car and you will usually find a “fuse map” written somewhere on the cover. If you don’t have it, take out the owner’s manual and look for it.
  • Step 2. If you don’t have a good fuse on hand right away, you can swap it with another one that is good in the fuse box. If that solves your problem, get a new fuse and put it back.

Fuse boxes could be located either under the hood of the vehicle or under the dashboard at the passenger side. Sometimes you may need to open the passenger door to find it.

Once you identify the tail light fuse, you could check it with a test bulb or multimeter. If the light bulb doesn’t light up, your fuse is faulty. This is also useful if you can’t visually see if the fuse is blown or not.

When buying a fuse:

Make sure that the new fuse you are getting is exactly the same amperage as the old one!

Also, fuses come in different sizes, so make sure you get the right size. If you can visually see a broken metal wire inside a fuse, this means that it is blown and you need to replace it.

If your problem persists and one fuse after another is getting blown, you have a problem with some kind of short in your electrical system. Take your car immediately to a shop and check it out!

If you are thinking of getting a bigger fuse, it will NOT solve your problem and is dangerous! Don’t do it!

#2. Your bulb needs replacement

After checking the fuses, if the problem is not solved, then the next logical thing to check is the actual light bulb. It is not as simple to check as a fuse, this is why we are doing the fuse first.

To check the light bulb, you will need to remove the tail light cover and remove the bulb from its socket. The next thing that you need to look at is the bulb’s filament (or wire inside the bulb).

If it’s NOT broken, then the bulb is NOT a problem. The broken filament inside the bulb is a sure reason why your tail light is not working!

#3. Bulb socket problem

It is a good idea to check out your socket after you pull out the tail light, so you don’t have to do it again. While at it, after taking the bulb out, use a multimeter to check if it is getting any current.

The most vulnerable part of the tail light construction is the socket that it gets placed in. Excess moisture builds up inside and it starts to rust.

If the socket is in a bad shape, you may need to replace it. Corrosion inside the light socket could result in bad contact between the bulb and a metal terminal.

In this case, it could be cleaned with a brush and WD-40. Also, check for any other obstructions in the light socket and remove them as well.

Put the bulb back into the socket and see if it works.

#4. Wiring problem

Bad wiring is a common problem in older cars and it could easily be a cause of your tail lights not working properly or at all. The cause of the bad wiring could be anything from excessive wear and tear to being melted if a short circuit occurred.

  • If your tail light is not getting any power, but there is power at the fuse, you could have a wiring problem between the socket and the fuse.
  • If there is NO power at the fuse, problematic wiring could be between the switch and the fuse.

Check different power-points between the light bulb and the battery and you will surely find where wiring could be messed up.

#5. New ground is needed

If your ground is broken, dirty, or loose, it may cause if a problem with the power delivery to your tail light. Any lamps in the car need to be grounded through some kind of mounting studs on the frame.

Here is a good explanation of how to fix your grounding problem:

#6. Your headlight control switch went bad

This switch controls NOT only headlights but tail lights as well since they come ON simultaneously. The malfunctioning control switch could be a cause of your tail light problem.

The contacts in the control switch can wear out and it will fail, leaving you without some kind of light. Another symptom of a failing control switch is that you may have problems switching between high and low beams.

If your headlights are NOT turning ON as well, this is a good indicator that the switch may be a problem. Lights (letters) around your transmission lever and around the radio may not work as well.

#7. Your daylight sensor went bad

In case you’ve got one of those newer cars with automatic light, if your ambient light sensor goes bad, it will not be able to tell if it is dark or light outside.

It is very useful if your car lights come ON automatically when it’s dark and go OFF when there is daylight, but if something with the sensor goes wrong, it could be stuck in either ON or OFF mode.

The most common location of the sensor is on top of the front windshield. Check the owner’s manual to see if you can override the system.

This does NOT happen very often, but if everything else fails, it is worth asking your mechanic to check this sensor.

#8. You installed a wrong light bulb

Did you just change a lightbulb and it’s not working? Sometimes it happens that you get the wrong type of lightbulb and your tail lights are not working.

Take a look at the part number of the new lightbulb and make sure it is compatible with your system. It doesn’t have to be the same brand as the old one, but it needs to be compatible.

This article is for informational purposes ONLY and is NOT a replacement for professional advice!


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