The third brake light, also known as the center high mount stop lamp (CHMSL), is a crucial safety feature on your vehicle. It provides an additional warning to drivers behind you when you're braking, significantly reducing the risk of rear-end collisions. Replacing a burnt-out or damaged third brake light is a relatively straightforward process that can be done at home with the right tools and knowledge, ensuring your safety and the safety of others on the road.
Here's a comprehensive guide to help you change your third brake light.
| Aspect | Details | Considerations |
|---|---|---|
| Tools Required | Screwdrivers (Phillips and flathead), socket set (various sizes), replacement bulb or LED assembly, gloves, safety glasses, masking tape (optional), multimeter (optional). | Ensure you have the correct screwdriver type and size to avoid stripping screws. A socket set is helpful for removing larger components. Using gloves protects your hands, and safety glasses protect your eyes. Masking tape can help protect surrounding surfaces. A multimeter can confirm power to the light. |
| Bulb Type & Size | Varies depending on vehicle make, model, and year. Common types include incandescent bulbs (e.g., 921, 168) and LED assemblies. Consult your owner's manual or an online bulb guide for the correct specification. | Using the incorrect bulb type or size can lead to improper illumination, electrical issues, or damage to the lighting assembly. LED assemblies offer improved brightness and longevity compared to incandescent bulbs. Always verify compatibility before purchasing. |
| Location of Light | Typically located inside the vehicle, mounted on the rear deck, rear window, or spoiler. Some vehicles may have it integrated into the trunk lid or liftgate. | The location significantly affects the access method. Interior-mounted lights usually require removing interior trim panels. Spoiler-mounted lights may require removing the spoiler itself. Trunk/liftgate-integrated lights often have access panels on the interior side of the trunk or liftgate. |
| Accessing the Light | Involves removing interior trim panels, unscrewing the light assembly, or detaching the spoiler (if applicable). Refer to your vehicle's service manual or online resources for specific instructions. | Patience is key when removing trim panels. Use trim removal tools to avoid damaging the plastic. Be careful not to disconnect any other wires or components accidentally. Take photos as you disassemble to aid in reassembly. |
| Removing the Old Bulb | Twist-and-lock or push-and-turn mechanisms are common. Some bulbs may simply pull out. Handle the bulb carefully to avoid breakage. | Allow the bulb to cool before handling to avoid burns. If the bulb is stuck, use a bulb removal tool or a cloth for better grip. Inspect the bulb socket for corrosion or damage. |
| Installing the New Bulb | Insert the new bulb into the socket, aligning it correctly. Ensure it's securely seated. | Avoid touching the glass portion of the bulb with your bare hands, as oils from your skin can shorten its lifespan. Use a clean cloth or gloves. If installing an LED assembly, ensure it's properly aligned and secured. |
| Testing the Light | Turn on the ignition and depress the brake pedal to verify that the new bulb is working correctly. | Have someone assist you or use a prop to hold the brake pedal down. If the light doesn't work, double-check the bulb installation, wiring connections, and fuse. A multimeter can be used to check for power at the bulb socket. |
| Reassembly | Reinstall the light assembly, trim panels, and spoiler (if applicable). Ensure all components are securely fastened. | Refer to the photos you took during disassembly to ensure everything is put back together correctly. Avoid over-tightening screws, which can damage the plastic. Test the brake light again after reassembly to confirm proper function. |
| Troubleshooting | If the new bulb doesn't work, check the fuse, wiring, and bulb socket. A multimeter can be used to diagnose electrical issues. | Refer to your vehicle's wiring diagram for the correct fuse location and wiring layout. Inspect the wiring for damage, such as cuts, frays, or corrosion. Clean the bulb socket with electrical contact cleaner if necessary. If you're unsure about electrical troubleshooting, consult a qualified mechanic. |
| Safety Precautions | Disconnect the negative battery terminal before working on electrical components. Wear safety glasses and gloves. Work in a well-lit and ventilated area. | Disconnecting the battery prevents accidental electrical shocks. Safety glasses protect your eyes from debris and broken glass. Gloves protect your hands from cuts and burns. |
| Estimated Time | 30 minutes to 1 hour, depending on the vehicle and the complexity of the access procedure. | Allow extra time if you're unfamiliar with the procedure or if you encounter any difficulties. Having the necessary tools and information readily available can significantly speed up the process. |
| Cost | Replacement bulb: $5 - $20. LED assembly: $20 - $100. Labor cost (if professionally installed): $50 - $150. | The cost of a replacement bulb or LED assembly varies depending on the type, brand, and source. Professional installation costs can vary depending on the labor rate and the complexity of the job. Doing it yourself can save you money on labor costs. |
Detailed Explanations
Tools Required: This refers to the specific instruments needed to complete the task. These include screwdrivers (both Phillips and flathead) to remove screws, a socket set for removing nuts and bolts, a replacement bulb or LED assembly, gloves to protect your hands, safety glasses to protect your eyes, masking tape (optional) to protect surrounding surfaces, and a multimeter (optional) to test electrical circuits.
Bulb Type & Size: This specifies the correct bulb for your vehicle. The third brake light bulb varies depending on the make, model, and year of your vehicle. Common types include incandescent bulbs (like 921 or 168) and LED assemblies. Always consult your owner's manual or an online bulb guide to ensure you purchase the correct bulb.
Location of Light: This indicates where the third brake light is situated on your vehicle. The light is typically located inside the vehicle, mounted on the rear deck, rear window, or spoiler. Some vehicles have it integrated into the trunk lid or liftgate. Knowing the location is crucial for determining how to access the light.
Accessing the Light: This involves the steps required to reach the bulb assembly. This may involve removing interior trim panels, unscrewing the light assembly, or detaching the spoiler (if applicable). Refer to your vehicle's service manual or online resources for specific instructions tailored to your car model.
Removing the Old Bulb: This describes the method for taking out the old, non-functioning bulb. Twist-and-lock or push-and-turn mechanisms are common. Some bulbs may simply pull out. Handle the bulb carefully to avoid breakage.
Installing the New Bulb: This explains how to correctly insert the new bulb. Insert the new bulb into the socket, aligning it correctly. Ensure it's securely seated. Avoid touching the glass portion of the bulb with your bare hands, as oils from your skin can shorten its lifespan.
Testing the Light: This step verifies that the new bulb is functioning correctly. Turn on the ignition and depress the brake pedal to verify that the new bulb is working correctly. Have someone assist you or use a prop to hold the brake pedal down.
Reassembly: This involves putting all the components back together in the correct order. Reinstall the light assembly, trim panels, and spoiler (if applicable). Ensure all components are securely fastened. Refer to the photos you took during disassembly to ensure everything is put back together correctly.
Troubleshooting: This section provides guidance if the new bulb doesn't work. If the new bulb doesn't work, check the fuse, wiring, and bulb socket. A multimeter can be used to diagnose electrical issues. Refer to your vehicle's wiring diagram for the correct fuse location and wiring layout.
Safety Precautions: These are essential measures to protect yourself during the process. Disconnect the negative battery terminal before working on electrical components. Wear safety glasses and gloves. Work in a well-lit and ventilated area.
Estimated Time: This is an approximation of how long the entire process should take. Typically, it takes between 30 minutes to 1 hour, depending on the vehicle and the complexity of the access procedure.
Cost: This provides an estimate of the expenses involved. A replacement bulb typically costs between $5 and $20. An LED assembly can range from $20 to $100. If you opt for professional installation, labor costs can range from $50 to $150.
Step-by-Step Instructions with Visual Aids (Where Applicable)
While providing actual visual aids here is not possible, imagine each step below accompanied by a clear photograph or diagram. This will greatly enhance understanding.
Step 1: Gather Your Tools and Materials
Before you begin, make sure you have all the necessary tools and materials readily available. This includes:
- A new third brake light bulb or LED assembly (check your owner's manual for the correct type)
- Screwdrivers (Phillips and flathead)
- Socket set (various sizes)
- Trim removal tools (optional, but highly recommended)
- Gloves
- Safety glasses
- Masking tape (optional, for protecting surrounding surfaces)
- Multimeter (optional, for testing electrical circuits)
Step 2: Disconnect the Negative Battery Terminal
This is a crucial safety step to prevent electrical shocks. Locate the negative battery terminal (usually marked with a "-" sign) and use a wrench to loosen the nut securing the cable. Carefully remove the cable from the terminal and tuck it away so it doesn't accidentally reconnect.
Step 3: Access the Third Brake Light Assembly
This step varies significantly depending on your vehicle's make and model. Here are some common scenarios:
-
Rear Deck Mounted (Inside the Car):
- Locate the access panel behind the rear seats or in the trunk.
- Use a screwdriver or trim removal tool to carefully remove the panel.
- You should now have access to the third brake light assembly.
-
Rear Window Mounted (Inside the Car):
- This often involves carefully prying away the headliner or trim surrounding the light assembly.
- Use trim removal tools to avoid damaging the plastic.
- Be patient and work slowly.
-
Spoiler Mounted:
- You may need to remove the entire spoiler to access the light assembly.
- Locate the screws or bolts securing the spoiler to the vehicle.
- Carefully remove the spoiler, being mindful of any wiring connected to it.
-
Trunk/Liftgate Integrated:
- Look for access panels on the interior side of the trunk or liftgate.
- Remove the panel to expose the light assembly.
Step 4: Remove the Old Bulb
Once you have access to the light assembly, you can remove the old bulb. There are typically two types of bulb sockets:
- Twist-and-Lock: Rotate the bulb socket counterclockwise to unlock it and then pull the bulb straight out.
- Push-and-Turn: Push the bulb in slightly and then rotate it counterclockwise to release it.
Handle the bulb carefully to avoid breakage. If the bulb is stuck, use a bulb removal tool or a cloth for better grip.
Step 5: Install the New Bulb
Insert the new bulb into the socket, aligning it correctly. Ensure it's securely seated. For twist-and-lock sockets, rotate the bulb socket clockwise to lock it in place. For push-and-turn sockets, push the bulb in slightly and then rotate it clockwise.
Avoid touching the glass portion of the bulb with your bare hands. Oils from your skin can shorten the bulb's lifespan. Use a clean cloth or gloves.
Step 6: Test the Light
Reconnect the negative battery terminal. Turn on the ignition and depress the brake pedal to verify that the new bulb is working correctly. Have someone assist you or use a prop to hold the brake pedal down.
If the light doesn't work, double-check the bulb installation, wiring connections, and fuse. A multimeter can be used to check for power at the bulb socket.
Step 7: Reassemble the Light Assembly and Trim
Reinstall the light assembly, trim panels, and spoiler (if applicable). Ensure all components are securely fastened. Refer to the photos you took during disassembly to ensure everything is put back together correctly.
Avoid over-tightening screws, which can damage the plastic.
Step 8: Final Test
Test the brake light again after reassembly to confirm proper function.
Troubleshooting Common Issues
- New bulb doesn't light up:
- Check the bulb: Ensure the bulb is the correct type and is not defective.
- Check the fuse: Locate the fuse for the third brake light in your vehicle's fuse box and check if it's blown. Replace it with a new fuse of the same amperage.
- Check the wiring: Inspect the wiring for damage, such as cuts, frays, or corrosion. Use a multimeter to check for continuity.
- Check the bulb socket: Clean the bulb socket with electrical contact cleaner to remove any corrosion or debris.
- Check the ground: Ensure the ground connection for the light assembly is clean and secure.
- Light is dim or flickering:
- Check the ground: A poor ground connection can cause dim or flickering lights.
- Check the wiring: Loose or corroded wiring connections can also cause these issues.
- Voltage drop: Use a multimeter to check for voltage drop in the wiring. Excessive voltage drop indicates a problem with the wiring.
- LED assembly doesn't work:
- Polarity: Ensure the LED assembly is connected with the correct polarity. Some LED assemblies are polarity-sensitive.
- Compatibility: Ensure the LED assembly is compatible with your vehicle's electrical system. Some vehicles may require a load resistor to prevent error messages or flickering.
Frequently Asked Questions
What is a third brake light and why is it important? The third brake light, or CHMSL, is an additional brake light that provides extra visibility to drivers behind you when you brake, reducing the risk of rear-end collisions.
How do I know what type of bulb my third brake light uses? Consult your vehicle's owner's manual or an online bulb guide to determine the correct bulb type and size for your specific make and model.
Is it difficult to change a third brake light myself? Replacing a third brake light is generally a straightforward process, but the complexity depends on the vehicle's design and the location of the light.
What tools do I need to change a third brake light? Common tools include screwdrivers, a socket set, a replacement bulb, gloves, and safety glasses. Trim removal tools and a multimeter can also be helpful.
What if the new bulb doesn't work after I install it? Check the bulb, fuse, wiring, and bulb socket. Use a multimeter to diagnose electrical issues. Ensure the bulb is correctly installed.
Conclusion
Changing your third brake light is a manageable task that can save you money and ensure your safety on the road. By following these detailed steps, taking necessary safety precautions, and troubleshooting common issues, you can confidently replace your third brake light and keep your vehicle in optimal condition. Always prioritize safety and consult a professional if you're unsure about any aspect of the process.