Brake Lights Not Working But Third Light Is (Causes & Fixes)

Are you facing a situation where your two brake lights don’t work but the third light works? If yes, you may have tried everything to fix this issue without success. And now you’re probably looking for suggestions on what could be wrong with your brake lights.

Brake lights not working but third light is usually occurs due to a variety of issues such as a burned-out bulb, blown fuse, faulty bulb socket, bad ground connection, wiring problems, or bad turn-signal switch. A bad brake light switch may also contribute to this issue.

In this article, we will discuss more details about this strange behavior of your vehicle brake light. We’ll cover all the potential causes behind this problem, and troubleshooting tips to help you fix the light and ensure your safety on the roads.

Why Are Your Brake Lights Not Working But Third Light Is?

If your car experiences a situation where only the top mount brake light works but the two lower ones don’t, several factors could be behind this problem.

Below, we’ll discuss the most common reasons you’re experiencing this problem:

• Burned-out bulbs: One of the reasons your primary brake lights stop working is due to bad bulbs. Each brake light usually has its bulb, so it is likely the two main brake light bulbs have burned out while the 3^rd one is still on. In this case, you’ll need to replace the bulbs to restore the functionality of these lights.
• Blown fuse: If you have a blown fuse for brake lights, it may be another reason for the lights to stop working. The fuses play a crucial role in regulating electricity flow to the brake lights. Thus, if it’s faulty, it will interrupt this flow and render the lights non-functional.
• Bad turn signal switch: If your vehicle uses the same light for turn signals and brake lights, then a faulty turn signal switch may be the culprit. When you press the brake pedal, the turn signal switch receives a signal from brake light switch and then triggers the brake lights to turn on. Therefore, if this turn signal switch is failing, it will not be able to send a signal to brake lights to illuminate.
• Wiring issue: The wiring that connects to these brake lights could also be having problems like damage, broken, loose, frayed, corroded, short-circuiting, etc. This can disrupt the electrical power flow and cause the lights to stop working. Still at it, issues with the wiring harness, connectors, and sockets can also affect electricity flow and make the lights non-functional.
• Poor ground connection: A bad ground connection may also make the lower stops on your car non-functional. The work of grounding is to provide a path for electricity to flow back to your car battery. Thus, if not properly connected, it may cause the brake lights to stop working.
• Brake light switch: Though a bad switch will affect all the lights, you may also want to check its condition. If the switch is misaligned or damaged, it will need to be replaced with a new one. Since the third stop light, the switch may not be the issue. Nonetheless, we still recommend checking it.

How To Fix Brake Lights Not Working But Third Light Is

Here are some helpful tips to troubleshoot and resolve the issue of brake lights not working but 3^rd brake light is:

• Start by checking the fuses for the lower brake lights. Test them for continuity. If they’re blown, replace them with new ones.
• Inspect the light bulbs. Take each bulb out and check if it has darkened or whether the filament inside is broken. These are key signs of a blown bulb. If the bulbs are bad, replace them with new ones.

NOTE: Sometimes the bulb and fuse may look fine but still not work, so the best thing is to test them. For instance, you should test the fuse for continuity or swap the bulbs with new ones to see if they work.

• If the bulbs and fuses are alight, inspect the bulb socket. Test the current at the sockets with the help of a digital multimeter while someone presses the brake pedal to see if you have wiring issues.

If there’s voltage, the bulb could be blown. If no voltage, consider repeating the test, but this time connect black test lead to ground (i.e., unpainted surface, bracket, bolt, etc.). If the voltage is registered, you have a poor socket ground connection.

However, if you still don’t get any voltage, inspect the bulb socket for loose wires, corrosion, and any signs of damage. Use a wire brush to remove any corrosion present.

• Trace and test the wires. Inspect the wiring for damage, short-circuiting, or loose connections. Check if the feed wire from brake light switch to the socket is loose or damaged. Test the wiring until you find where there’s a break and fix it.

Check the video below on how wiring faults can lead to malfunctioning brake lights:

Video:

• If you still haven’t resolved the issue, you may want to troubleshoot the turn signal switch and brake light switch for problems. (More details on how to test these two switches coming up below).

How Do You Know If Your Turn Signal Switch Is Bad?

If you suspect your turn signal to be behind the lower brake lights not working, you can test it by following the procedure below:

Step 1. Check your vehicle turn signal switch wiring diagram on your owner’s manual. Note the wiring running from brake light switch to the turn signal switch.

Step 2. Access the electrical connector for the turn signal switch. In most cases, you’ll need to remove the cover on your steering column to access this component. Find the wire you noted in Step 1.

Step 3. Press your brake pedal to activate brake light switch. Alternatively, you can unplug the switch electrical connection and use a jumper wire to connect the two terminals

Step 4. Now grab a test light and back probe the brake light switch wire at the electrical connector. If this light doesn’t glow, then a problem exists between brake light switch and the turn signal switch. In this case, you should inspect the connector and wires running from the signal switch to brake lights.

Step 5. Now press the brake pedal again or use the jumper wire method, and back probe the terminals carrying current from signal switch to the right and left turn signal lights. If the test light glows, it means the switch is good. If not, the switch is bad.

Note that this test applies to cars that use combined brake and signal light switch.

This video shows how to troubleshoot turn signal switch in a car where only 3^rd brake light is working:

Video:

How Do You Know If Your Brake Light Switch Is Bad?

Malfunctioning brake light switch usually affects all the brake lights, including the third brake light.

However, if none of the troubleshooting above solves the problem, you may want to check if your brake light switch has any issues.

Here are steps for troubleshooting the brake light switch:

Step 1. Locate your brake light switch position. In most cases, the switch is located atop the brake pedal assembly. In some car models, the switch may be positioned around master cylinder, on firewall inside engine compartment on the driver’s side.

Note that vehicles with cruise control may have two brake light switches.

Step 2. Once you have found the switch, you should then locate its electrical connector.

Step 3. Now you’ll need to use a test light to test this switch. Connect this light to proper ground under your car dash.

If your switch already connects to a module, e.g. body control module (BCM), then it provides good ground connection for the module. So just connect the test light to power source, e.g. battery. If necessary, consult your vehicle repair guide.

Step 4. If you can easily access the switch electrical connector, you can back probe its terminals at the connectors without necessarily unplugging the connector. Otherwise, you’ll need to unplug the connector to probe each terminal.

Step 5. The test light ought to illuminate when you probe one of the terminals only. If it doesn’t, it means the power side of your circuit (or ground, depending on your car configuration) has short or open circuit. In this case use, you can use your repair manual to locate the fault on this circuit side.

Step 6. If the test light illuminates, press the brake pedal firmly while you back-probe the switch connector. The light ought to come on while testing both terminals. If it only illuminates when you probe just one terminal, then the switch is misadjusted or faulty.

Step 7. If you unplugged the electrical connector for the switch, try using a small jumper to connect the two terminals. If the brake lights come on, it means you’ll need to adjust or replace your brake pedals.

Can You Drive With Only The Third Brake Light?

While you can drive with only the third brake light, we don’t recommend it. The third brake light only acts as additional brake light mounted higher than primary stoplights. This makes it easily visible to distracted drivers, or in heavy traffic or poor weather.

With the lower brake lights off, the drivers may not be able to tell when you’re braking or coming to a stop. This increases your risk of getting rear-ended.

Moreover, it’s against the law to drive with your lower brake lights not functioning. You’ll be pulled over by cops and even get citations or fines.

Therefore, if your traditional brake lights are malfunctioning, we advise you to fix them promptly so that you can drive with peace of mind knowing you’re visible to other road users.

If you’re facing the issue of your brake lights not working but the third light is functioning correctly, it’s crucial to identify the underlying cause and resolve it promptly. For a more detailed understanding of this issue and possible solutions, we recommend reading our article on third brake light not working. Additionally, if you’re experiencing a related problem specifically with the left turn signal and brake light not working on your trailer, you may find our article on left turn signal and brake light not working on trailer helpful in troubleshooting and resolving the issue.

FAQs:

Conclusion

If your car experiences the issue of brake lights not working but the third light is, the potential causes to consider include blown bulbs, blown fuse, wiring problems, and grounding problems. Failing multi-function switch or turn signal switch and brake light switch are additional potential culprits to consider.

This article has highlighted all these common causes and how to troubleshoot your car for this problem. We advise you to fix your brake lights as soon as possible to ensure maximum safety on the road. If you’re unable to resolve the issue on your own, don’t hesitate to consult your mechanic or dealership.