Third Brake Light Not Working? Here's How to Fix It
The center brake light is out but your left and right ones are fine. It's usually a bulb, a dead LED strip, or a bad socket. Here's how to work through it.
How the Third Brake Light Works
The center high-mount stop lamp (CHMSL) sits above the rear window on sedans and at the top of the hatch on SUVs and wagons. It gets power from the same brake light switch as your other two brake lights, triggered every time you press the brake pedal.
Older vehicles use a standard incandescent bulb in a simple socket. Most vehicles from the mid-2000s onward use an LED strip or array sealed inside the housing. The two types fail differently and require different fixes.
Because the CHMSL is at eye level for the driver behind you, it's actually one of the more important brake lights on your car. It's also federally required, so a failed one can get you pulled over.
Start Here: Narrowing Down the Cause
Before pulling anything apart, answer two questions.
Are your other two brake lights working?
Have someone press the brake pedal while you watch from behind the car. If the left and right brake lights light up but the center one doesn't, the problem is isolated to the CHMSL circuit or housing. The brake light switch and the main fuse are both fine. You're looking at a bulb, LED strip, socket, or a break in the wiring running specifically to that housing.
If all three brake lights are out at the same time, that's a different problem. The brake light switch or a blown fuse is more likely. Head to the brake light switch and fuse box first.
Is it completely dead or just dim and flickering?
A completely dark CHMSL points to a dead bulb, failed LED array, blown dedicated fuse, or broken wire. A light that's dim, flickering, or works only sometimes is almost always a connection problem: a loose bulb, a cracked flex connector in the trunk lid wiring, or corrosion on the socket contacts.
Check the Bulb First (Incandescent Vehicles)
If your vehicle uses a traditional bulb in the CHMSL, this is your first stop. Access to the socket varies by vehicle:
- Sedan: Open the trunk and look up toward the rear window. You'll usually see a trim panel or the back of the CHMSL housing. Pull back the trunk liner near the top rear to expose the socket. Some sedans have a removable access panel in the parcel shelf.
- SUV or hatchback: Open the hatch and look at the inside face of the hatch door near the top. Peel back the trim panel to reach the wiring and socket.
- Pickup truck: The CHMSL is usually in the cab above the rear window. Access is from inside the cab by removing the headliner trim near the back glass.
Once you have the socket, twist it counterclockwise or pull it straight out depending on the mount type. Pull the bulb and look at it in good light. A broken filament or dark smoky glass means it's blown. Install a replacement that matches the base type and wattage. If you can't read any markings on the old bulb, take it to the parts store and match it by size.
After installing the new bulb, press the brake pedal and verify the light works before putting the trim panels back.
LED Strip Failure (Most Post-2010 Vehicles)
If your vehicle has an LED third brake light, there's no bulb to swap. The LEDs are either mounted on a replaceable strip inside the housing, or they're permanently bonded into a sealed assembly.
Replaceable LED strip
Many manufacturers design the CHMSL with a LED bar or strip that can be unplugged and swapped. To check yours: remove the housing from the vehicle (usually two or three screws and a wiring connector), then look for a separate LED board inside the housing that has its own connector. If you see a plug, the strip is replaceable. Search your year and model online for the LED strip part number. Installation is usually plug-and-play once you have the housing off.
Sealed LED assembly
On sealed assemblies, the LEDs are integrated into the housing and can't be replaced separately. When the LEDs go, the whole housing gets replaced. This is more common on factory OEM units. Aftermarket replacements for most vehicles run $20 to $80 and are a direct swap.
You can tell which type you have by looking up the part on RockAuto or a similar site. If a standalone LED strip is listed separately from the full assembly, your vehicle uses the replaceable type.
Check the Fuse
Most vehicles run the CHMSL off the same fuse as the other brake lights. If the left and right brake lights still work, the main brake light fuse is almost certainly fine. But some vehicles have a separate fuse dedicated to the center lamp.
Open your owner's manual to the fuse box diagram and look for any fuse labeled "CHMSL," "CHMSL LAMP," "HIGH MOUNT," or "STOP LAMP HIGH." Pull it and check whether the metal strip inside is intact. If it's broken, replace it with one of the same amperage.
If you install a new fuse and it blows immediately when you press the brake pedal, there's a short in the CHMSL circuit. Don't keep replacing fuses. Track down the short in the wiring between the fuse box and the housing before replacing any more fuses.
Wiring and Connectors
If the bulb or LED and the fuse are both good, the problem is in the wiring. There are two spots to focus on.
The trunk hinge flex connector
On sedans with a hinged trunk lid and SUVs with a tailgate, the wiring to the CHMSL passes through a rubber boot or flex loom at the hinge. Every time you open and close the lid, that wiring flexes. Over years of use, the insulation cracks and wires break inside the boot, even when the outside of the wire looks fine.
Find the rubber flex connector between the body and the trunk lid at one of the hinges. Open the trunk partially and flex the boot by hand while someone watches the CHMSL. If the light flickers or comes on, there's a broken wire inside. Replacing the flex connector wiring is a moderately involved DIY job but is very commonly done on higher-mileage vehicles.
The socket connector
On incandescent CHMSL setups, check the wiring connector that plugs into the socket. Unplug it and look at the terminals inside. Corroded or pushed-back terminals cause poor contact and intermittent failures. Clean corroded pins with electrical contact cleaner and a small pick. If any terminal is pushed back or bent out of shape, carefully press it back into position. Plug it back in firmly and test before reassembling.
When You Need a New Assembly
In some cases, the housing itself is why the light isn't working.
- Sealed LED assembly with a dead LED array. If yours is a sealed unit and the LEDs are gone, there's no bulb to change. The assembly is the repair.
- Cracked or water-damaged housing. A housing with a crack in the lens lets in moisture. Water inside an LED assembly corrodes the circuit board and kills individual LEDs. The damage is ongoing even after you dry it out, so replacing the housing stops the cycle.
- Melted or burned socket area. A bulb of the wrong wattage or a loose socket that arced can melt the plastic around the socket. A new bulb won't seat correctly in a melted socket. Replace the housing.
Aftermarket CHMSL assemblies for most vehicles run $20 to $80. Removal is typically two to four screws and a wiring connector, and the whole job takes under 30 minutes on most vehicles.
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