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Tail lights and brake lights are located at the rear end of the vehicle. Both are usually covered by a single external housing一but does that mean they’re technically the same? Let’s find out. 

What’s the Difference Between Tail Lights and Brake Lights?

The main difference between tail lights and brake lights is that the former lights up as soon as the headlights are turned on, while the latter only engages upon stepping on the brake pedal. While both lights are red, brake lights tend to emit a more luminous red light.

Close up of car tail light
One filament inside the bulb is for the tail light and the other filament is for the brake light.

Are My Tail Lights and Brake Lights Using the Same Bulb? 

On many vehicles, the tail lights and brake lights share the same bulb. One filament inside the bulb is for the tail light and the other filament is for the brake light. There are also some vehicles that have a separate bulb for each circuit.

You can determine whether your brake lights and tail lights share the same bulb by having an assistant press the brake pedal and noting which bulb illuminates within the tail light assembly.

As an aside, on most vehicles, the brake lights (stop lights) double as turn signals. Typically, the stop lamps are wired through the turn signal switch and its flasher or module so that when the stop lights are activated and a turn signal is selected, the stop light on that side of the car will flash. Exceptions would be vehicles with stand-alone turn signals, which are usually orange rather than red and only serve as turn signals or hazard flashers.

The tail lights, on the other hand, may share the same bulb but aren’t as bright as the turn signal/brake lights, which are brighter and pull more current.

How to Check Your Rear Lights

Your vehicle’s tail lights and brake lights are essential safety components not only for you but for other drivers as well. These lights allow your vehicle to be seen during low-visibility conditions and alert other drivers that you’re slowing down, so it’s important to ensure they’re working properly before driving.

On many vehicles, the tail light circuit also feeds the instrument lamps, so that if the tail lamp fuse is blown, the instrument lamps are also inoperative. On vehicles wired this way, the instrument lamps will have a separate fuse between the tail light circuit and the instrument panel lamps.

To check if your rear lights are working, turn on the headlights. The tail lights should glow red once they’re on. Next, have someone stand behind your vehicle to check the brake lights. They should shine brighter than the tail lights once you step on the brake pedal.

What Causes Rear Lights to Fail?

There are several reasons that may cause a tail light or brake light to fail. These include:

Burnt Bulb

A burnt bulb is one of the most common reasons for tail lights and brake lights to fail. If you notice your tail lights aren’t working but the brake lights are (and vice versa), it may be time for a bulb replacement. 

Circuit Problems 

Circuit problems, such as damaged wiring and corroded bulb sockets, can result in inoperative rear lighting.

If you have wired a lot of other lights (trailer lamps, aftermarket running board or clearance lamps, etc.) to your tail lamp wiring circuit, the part of the headlight switch that feeds the tail lamps can fail due to overheating. The OEM tail light wiring can also fail and melt its way into other wires. This happens more than you think. Aftermarket wiring should include a relay to carry the extra load.

Blown-Out Fuse

If a fuse blows out, power is cut off from the lights, preventing them from turning on.

car brake light switch
If your brake lights stay on after you’ve stopped stepping on the brake pedal, you may be dealing with a bad brake light switch.

Faulty Brake Light Switch 

If your brake lights stay on after you’ve stopped stepping on the brake pedal (or they don’t come on at all with the pedal depressed), you may be dealing with a bad brake light switch. In some cases, the switch contacts may stick t, causing the switch to continuously supply power to the brake lights even when you’re not stepping on the brake pedal.

The brake light switch may also slip out of position, create a space between its plunger and the pedal, and prevent the switch from being turned off.

Get Your Tail Lights Installed. Get $100 Cash Back.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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