If one or all of your brake lights isn’t working, it can be a cause for alarm. After all, brake lights are an essential part of driver communication while on the road. You’ll earn a traffic ticket if one or all of them are inoperative. The minute you notice one of your brake lights is on the fritz, you ought to look into it. Here are some troubleshooting tips for how to test brake lights.
Brake Light Issues and What To Check
Most modern vehicle brake lights operate either through a switch mounted to the brake pedal or a hydraulic switch on the brake line or master cylinder. The switch connects to a 12V power source protected by a fuse. When you press on the brakes, power is sent to the other side of the fuse, which closes the circuit and triggers the brake light bulbs at the same time as the brakes.
When something in the brake light system goes awry, the brake lights stop functioning normally. We’ve listed the different common issues you might encounter and how you or your mechanic can troubleshoot each problem’s potential causes.
One or More Brake Lights Not Working
If one or more brake lights aren’t working, but the other lights are operational, you can likely blame faulty bulbs, fuses, or sockets.
Bulbs
Checking and changing out your vehicle’s brake light bulbs is pretty simple. You’ll usually need to go through the vehicle’s trunk or fender to remove the casing or bulb trim. Afterwards, unscrew the bulb and inspect it for damage. If you see damage on the bulb’s housing or filament, it’s time for a new bulb. You can check your vehicle’s manual for details on how to reach the bulbs and what kind of replacement bulbs you need to buy.
Sockets
Sockets are another point of failure for individual bulbs. You can typically reach them the same way you reached the bulbs. Depending on your vehicle though, further testing might require more disassembly. It can become a very complicated procedure very quickly because you’re working with the electrical system, so be careful and take your vehicle to the auto repair shop if you aren’t confident with your DIY abilities.
You can check the brake light sockets visually for discoloration, contact corrosion, or distortion. You can also check their voltage using a voltmeter. Have a friend depress the brakes and touch the socket’s terminals with a voltmeter. If there’s no voltage, probe the wires behind the socket. Be careful not to damage the wire, or it’ll cause more issues down the line.
If there’s no voltage at all from the wire, you can likely blame a bad turn signal switch or a broken connector. If there’s voltage between the wires and ground, check the ground wire for continuity with an ohmmeter. If there’s continuity, replace the whole socket.
Wires and Connectors
If power isn’t even reaching the socket, it’s possible that the wires and connectors in the system are to blame. It’s best to trust a professional auto electrician with inspecting and repairing the wires and connectors linking your vehicle’s brake lights to the rest of the electrical system. They have access to wiring diagrams for different vehicle systems, and can adequately test and replace pertinent parts. They can check that the right amount of voltage is flowing through the socket wires, and check for voltage along the circuits.
All Brake Lights Not Working
If all your vehicle’s brake lights aren’t working, it’s time to check the fuses, brake light switch, and also look for possible electrical grounds in the system.
Brake Light Fuse
If all your brake lights aren’t working, your vehicle likely has an electrical system issue. If a busted fuse is to blame, you’re in luck. It should be a quick fix. The brake light system’s fuse protects it from amperage overloads. If an electrical component blows out, the fuses protect the rest of the vehicle from frying. A failed fuse does also keeps electricity from reaching your lights though.
You can check your vehicle’s fuse box either under the dashboard or the hood. Your vehicle’s manual should indicate the brake light fuse’s position. Grab a test light and press one end to a ground source. Then, press the tester’s tip to the fuses’ ends one at a time. Have a friend press gently on the gas pedal while the vehicle’s parking brake is engaged. If the light illuminates on both ends, the fuse is good and the problem lies elsewhere
If the light illuminates on only one side of the fuse though, that points to a faulty fuse. The same goes if the test light doesn’t illuminate at all. Pick up a replacement fuse with the same amp rating, and once you replace the fuse, you can test it again. Once both ends trigger a light, you’ve repaired the broken brake light switch.
It’s best to have an auto electrician check for electrical system issues in other parts of the system if the brake light fuse regularly fails. A blown fuse is often a sign of further issues.
Brake Light Switch
You can also check the vehicle’s brake light switch if the fuse and brake light bulbs aren’t working. The brake light switch is a basic two-wire switch that connects and completes the brake light circuit. You can find the switch near the brake pedals and test it using a test light. One end of the test light should go on the ground, and the sensor should link to one of the switch’s two wires. If the bulb lights up, the switch is fine. Replace the switch if the light doesn’t illuminate.
More complicated systems with more than two wires exist, and you might need to check your vehicle’s owner’s manual to find the proper “power in” and “power out” wires to test.
Electrical Ground
It’s possible that electrical grounds are to blame for your brake lights not working. Grounds happen when the power gets redirected away from the circuit and to a ground, keeping the power from reaching the lights. A bit of corrosion along a wire is all it takes for a ground. A professional mechanic can search for grounds throughout your vehicle’s electrical system using a voltmeter set to Continuity or Ohms.
Brake Light Not Turning Off
If your vehicle’s brake light stays on even when the brake isn’t depressed, check the brake light switch or sensor. A faulty brake pedal or incorrect bulbs can also cause this issue.
Turn Signal Turns On Instead of Brake Light
If the turn signal engages instead of your vehicle’s brake lights when you depress the brakes, look at the bulbs, brake light switch, and the sockets.
Now you know how to troubleshoot brake lights that’re not working. Remember to bring your vehicle to a professional mechanic if you need to. You might be able to repair your brake lights yourself, but it’s always safer to go with the professional option if you aren’t sure of your DIY abilities.
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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.
