The rear or tail lights are a safety feature on your automobile. They become even more important while driving at night, low visibility conditions such as fog, storms, rain, and other bad weather.

The taillights indicate the size and shape of your vehicle besides your position on the road to other drivers.  These lights illuminate brighter when you are applying brakes. This indicates to the person behind you to stop or slow down and change their path. During the day the headlights are off and only the rear lights are used to indicate that the driver is applying brakes.

The taillights come on when your headlights are on or your parking brake is engaged. The brake lights turn on when you apply pressure on the brakes. In most automobiles, the taillights are red while the brake lights are a brighter, more luminous red.

The rear lights are controlled by the same switch as the headlights. The power flows through a relay to the rear lights when the switch is turned on. While the brake light switch is connected to the brake pedal which comes on when the pedal is pressed. When the tail lights fail or do not function properly the car becomes a danger or hazard to self and others on the road. You may receive a ticket or citation from the traffic police.

The Causes Why Tail Lights Not Working

The common causes the tail lights do not work are;

Blow fuse – The first thing the mechanics check is the fuse corresponding to the rear lights. When the fuse is 4 Causes Why Tail Lights Not Working but Brake Lights Are in 2020blown it does not allow the circuit to complete. As the rear lights are not connected, they do not illuminate.

A fuse is a band of metal alloy inside a plastic container It is designed to break in the event of a power surge. When the band melts the circuit breaks and protects the electrical system and the lights from damage.

Fuses are located in two regions of the car;

One is situated inside the cabin. Here the fuse panel is on the passenger side underneath the dash behind the plastic panel. In some automobiles, they may be on the side of the dashboard allowing the passenger side door to open all the way.

The other common situation of the fuse box is under the hood. It is mostly a large black box with many wires connected to it. To access the fuses, you have to take off the lid.

Each of these fuses controls a different component. Their function is usually enlisted on the cover. If it is not indicated there then consult the car manual. You will find the year, the model-specific make specified on the diagram.

When you have located the fuse for the tail lights use a fuse tester to check the connection. If the tester lights up – your fuse is functioning fine. If it does not light up then, replace the fuse with another of the similar amperage and size. In many instances, you can see the break in the metal strip of the fuse.

Burnt out light bulbs – The other reason your tail lights are not working but your headlights are maybe a blown bulb. When the filament inside the bulb breaks it cannot illuminate the gas enclosed within the glass cover. This burnt-out bulb does not affect the circuitry of the light system and it continues to function normally.

You may have to remove the cover of the tail light. In some cars, there is an access panel that has to be removed to reach inside to twist out the spent bulb.4 Causes Why Tail Lights Not Working but Brake Lights Are in 2020

Unscrew the bulb and inspect it closely to check if the filament is broken. The high resistance filament is placed between to electrodes that glow when current is passed through this system. This glow is the red tail light. A broken filament will not produce any light thus you will have to replace it with a new bulb.

Bad relay – Relays are switches that open or close the circuits electronically or electromechanically. They control one electrical circuit by shutting or opening connections in another circuit. A relay controls the power flowing through a system. Automatic relays automate this function where power flows are on or off at particular times.

In this case, the relay will transfer power from the battery to the taillights. But when it fails – the connection is not completed. This may happen because the relay is not grounded correctly. An improperly grounded wire can cause excess charge to build up in the system and cause a short circuit.

There may be broken wires along the relay system. To correct this, you may have to obtain the diagram to visually inspect the system. The wiring going to the tail lights may be damaged or broken with cracks in the insulation. The ground wire should not be broken or cut as this will not deliver electricity to the sockets in which the bulb is fitted.

Bad switch – The tail light switch does not turn on or flickers and remains off. This is an indication of the wires not connected correctly to the switch. Usually, the switch turns on the taillights, the headlights and parking lights 4 Causes Why Tail Lights Not Working but Brake Lights Are in 2020are connected to this switch.

If the relay is correct, the wires and the bulb’s filament are intact then this may be the issue. You can pull out this assembly and checked with a multimeter for issues. If the rear light lights up correctly but does not become bright when the brake is applied then the switch of the brake is faulty.

This circuit is connected with the brake pedal – if the switch is out of place or connected incorrectly then the pedal may not be able to complete the circuit correctly.


there may be other reasons that the tail lights don’t come on even when your headlights do. The socket which holds the bulb may have failed. These are conductive surfaces that help the passage of electricity. The socket fails with moisture enters – this may also cause rusting. The rusting may also break the connection with the wire in the back. Inspect the socket for discoloration – brown, black, whitish, etc. Check if there are dislocated, bent or broken pins. Then use a multimeter in the socket to check the passage of electricity. If electricity is not reaching the pins than there is a failure in the passage of current somewhere in the electrical system.

The latest cars have ambient light sensors. The on-board computer turns on the tail and headlights according to the light outside the car. If it is dawn or dusk the head and tail lights will come on by themselves. The light sensors also switch off the daytime lights in some latest models. When the sensor is dirty or damaged it cannot tell if it is dark or day outside. If your parking and headlights do not turn on but the brake lights do – the ambient light sensor is the culprit.

Overall tracking the causes why tail lights not working but brake lights are is frustrating. But thankfully as the taillights run on their isolated circuit there should not be any problem to track the issues. Besides, you are secure as the brake lights are connected to the pedal and are connected to another circuit. Thus, the brake lights will come one when you press the brakes.