How To Fix High Mounted Brake Light

The high-mounted brake light, often called the third brake light or center high mount stop lamp (CHMSL), is a crucial safety feature on your vehicle. It provides an additional visual cue to drivers behind you when you're braking, helping to prevent rear-end collisions. When it malfunctions, it's essential to address the problem promptly to ensure your safety and the safety of others on the road. This article outlines the most common issues, their causes, and the steps you can take to diagnose and fix a faulty high-mounted brake light.

Symptoms of a Faulty High-Mounted Brake Light

The symptoms of a malfunctioning high-mounted brake light can vary, but here are the most common indicators that something is wrong:

Complete failure: The most obvious symptom is the light not illuminating at all when the brake pedal is pressed.
Intermittent operation: The light might work sometimes but not others, making it unreliable. This is a particularly dangerous situation because drivers behind you can't consistently rely on it.
Dim or flickering light: The light might illuminate, but it's significantly dimmer than usual, or it flickers. This reduces its visibility, especially in bright sunlight.
Other brake lights malfunctioning: While not always directly related, a problem in the brake light circuit can sometimes affect other brake lights or even the entire rear lighting system. Check all your brake lights if you notice a problem.
Warning light on the dashboard: Some vehicles, particularly newer models, have a dashboard warning light that indicates a problem with the brake lights. Refer to your owner's manual for specific information about your vehicle's warning lights.

Root Causes of High-Mounted Brake Light Problems

Several factors can contribute to a malfunctioning high-mounted brake light. Understanding these causes is the first step towards diagnosing the problem:

Burnt-out bulb: This is the most common reason. The bulb, like any other light bulb, has a finite lifespan and will eventually burn out.
Faulty wiring: Damaged or corroded wiring can prevent the electrical current from reaching the bulb. This can be due to age, exposure to the elements, or physical damage. Look for frayed wires, cracked insulation, or corroded connectors.
Defective socket: The bulb socket itself can become corroded or damaged, preventing a good electrical connection. This is especially common in older vehicles or those exposed to moisture.
Failed brake light switch: The brake light switch, usually located near the brake pedal, activates the brake lights when the pedal is pressed. If this switch fails, it can prevent all brake lights, including the high-mounted one, from working.
Blown fuse: A blown fuse in the brake light circuit can cut off power to the high-mounted brake light. Check the fuse box for any blown fuses related to the brake lights.
Problem with the vehicle's computer (ECU): In rare cases, a problem with the vehicle's computer (ECU) can affect the brake light system. This is more common in newer vehicles with complex electronic systems.
Water intrusion: Leaks around the high-mounted brake light housing can allow water to enter and corrode the electrical connections, leading to malfunction.

What Happens If Ignored?

Ignoring a faulty high-mounted brake light can have serious consequences:

Increased risk of rear-end collisions: The high-mounted brake light provides a crucial visual cue to drivers behind you, especially in stop-and-go traffic or during adverse weather conditions. A non-functioning light significantly increases the risk of being rear-ended.
Legal consequences: In many jurisdictions, it's illegal to operate a vehicle with a malfunctioning brake light. You could receive a ticket or citation.
Failed vehicle inspection: Many states require vehicles to pass a safety inspection. A faulty brake light will likely cause your vehicle to fail the inspection, preventing you from renewing your registration.
Reduced resale value: A well-maintained vehicle is more valuable. Fixing a faulty brake light is a simple and inexpensive way to maintain your vehicle's value.

Recommended Fixes

The appropriate fix depends on the underlying cause of the problem. Here's a breakdown of the most common solutions:

Replace the bulb: This is the simplest and most common fix. Refer to your owner's manual to determine the correct bulb type. Before replacing the bulb, ensure the ignition is off and the brake pedal is not depressed.
Steps:
1. Access the high-mounted brake light assembly (usually from inside the vehicle's cabin or the trunk).
2. Remove the lens cover.
3. Remove the old bulb (usually by twisting or pulling it out).
4. Install the new bulb.
5. Reinstall the lens cover.
6. Test the light to ensure it's working.
Repair or replace faulty wiring: If the wiring is damaged, you'll need to repair or replace it.
Steps:
1. Visually inspect the wiring for any signs of damage.
2. Use a multimeter to test for continuity in the wiring.
3. If the wiring is damaged, repair it by splicing in new wire or replace the entire wiring harness.
4. Ensure all connections are secure and protected from the elements.
Clean or replace the bulb socket: If the bulb socket is corroded, try cleaning it with a wire brush or electrical contact cleaner. If the corrosion is severe, you may need to replace the socket.
Steps:
1. Disconnect the wiring from the socket.
2. Clean the socket with a wire brush or electrical contact cleaner.
3. If necessary, replace the socket with a new one.
4. Reconnect the wiring to the socket.
Replace the brake light switch: If the brake light switch is faulty, you'll need to replace it.
Steps:
1. Locate the brake light switch near the brake pedal.
2. Disconnect the wiring from the switch.
3. Remove the old switch.
4. Install the new switch.
5. Reconnect the wiring to the switch.
6. Adjust the switch if necessary (refer to your vehicle's service manual).
Replace a blown fuse: Check the fuse box for any blown fuses related to the brake lights and replace them with a new fuse of the same amperage. Important: If the fuse blows again immediately, there may be a short circuit in the wiring.
Steps:
1. Locate the fuse box (usually under the dashboard or in the engine compartment).
2. Identify the fuse for the brake lights (refer to the fuse box diagram).
3. Remove the blown fuse.
4. Install a new fuse of the same amperage.
Address water intrusion: Seal any leaks around the high-mounted brake light housing to prevent water from entering and causing corrosion. You may need to replace the gasket or sealant.
Steps:
1. Inspect the high-mounted brake light housing for any signs of leaks.
2. Remove the housing.
3. Clean the area around the housing.
4. Apply new sealant or replace the gasket.
5. Reinstall the housing.
Consult a professional: If you've tried the above fixes and the problem persists, or if you suspect a problem with the vehicle's computer, it's best to consult a qualified mechanic.

Cost Estimates and Shop Advice

The cost of fixing a high-mounted brake light can vary depending on the problem and whether you do it yourself or take it to a shop.

Bulb replacement: A replacement bulb typically costs between $5 and $20. The labor cost for a shop to replace the bulb is usually minimal, often around $20-$50.
Wiring repair: The cost of wiring repair can vary depending on the extent of the damage. A simple repair might cost $50-$100, while replacing an entire wiring harness could cost several hundred dollars.
Bulb socket replacement: A new bulb socket typically costs between $10 and $30. The labor cost for a shop to replace the socket is usually around $50-$100.
Brake light switch replacement: A new brake light switch typically costs between $20 and $50. The labor cost for a shop to replace the switch is usually around $50-$150.
Fuse replacement: A new fuse typically costs a few dollars.
Water intrusion repair: The cost of repairing water intrusion can vary depending on the severity of the leak. Simple sealant application might cost $50-$100, while replacing the entire high-mounted brake light assembly could cost several hundred dollars.

Shop Advice: When taking your vehicle to a shop, be sure to get a written estimate before any work is performed. Ask the shop to explain the problem and the proposed solution in detail. If you're unsure about something, don't hesitate to ask questions. A reputable shop will be happy to answer your questions and provide you with all the information you need to make an informed decision.

Credibility and Additional Information

While there are no specific TSBs (Technical Service Bulletins) that cover every high-mounted brake light issue (they tend to be model-specific), keep an eye out for recalls or TSBs related to your vehicle's brake light system. You can search the National Highway Traffic Safety Administration (NHTSA) website for recalls and TSBs related to your vehicle. Many online forums dedicated to specific vehicle makes and models also contain discussions about common brake light problems and solutions. Reviewing these forums can provide valuable insights into potential issues specific to your vehicle.

Many vehicles, particularly those built after the mid-2000s, use LED high-mounted brake lights. These lights are generally more reliable than traditional incandescent bulbs, but they can still fail. When an LED light fails, it usually requires replacing the entire light assembly, as the LEDs are often integrated into the unit. Consider this when budgeting for repairs.

Addressing a faulty high-mounted brake light is a simple but vital task that can significantly improve your safety on the road. By understanding the common causes and solutions, you can diagnose and fix the problem yourself or seek professional help with confidence.