If you're looking to upgrade your rear end, adding an frs 4th brake light is probably one of the first mods on your list. It's one of those projects that doesn't cost a fortune but completely changes the vibe of the car. Honestly, if you own a Scion FR-S, Subaru BRZ, or a Toyota 86, you've probably stared at that weird plastic triangle in the middle of your rear bumper and wondered why it doesn't do anything. In North America, it's just a placeholder, which feels like a missed opportunity for such a driver-focused car.
Most people start their modding journey with things like wheels or an exhaust, but lighting is where you can really show some personality. The factory setup is fine, but it's a bit safe. Adding that fourth light fills in the "missing piece" of the design and gives the car a much more aggressive, finished look. Plus, it actually serves a purpose by making you more visible to the person tailgating you in traffic.
Why Everyone Swaps the Rear Fog Housing
The stock "light" on the FRS is basically just a reflector or a plastic plug, depending on your trim level. In other parts of the world, like Europe or Japan, that spot is used for a rear fog light. Because of US regulations or just cost-cutting measures, we got the short end of the stick. Replacing that dead space with a functional frs 4th brake light is almost a rite of passage for owners.
There's also the safety aspect. These cars are low. Like, really low. If you're sitting behind a massive SUV in stop-and-go traffic, a little extra illumination at eye level for them isn't a bad idea. Most aftermarket 4th brake lights come with a strobe or "F1-style" flash feature. When you hit the brakes, it blinks a few times before staying solid. It's a great way to grab attention and make sure people know you're stopping.
Choosing the Right Style for Your Build
Once you decide to go for it, you'll realize there are way more options than you expected. It's not just "red or clear" anymore. You've got different lens colors, LED patterns, and housing styles.
The Classic Red Lens
If you want to keep things looking OEM+, the red lens is the way to go. It matches the factory tail lights perfectly. It looks like it belongs there from the factory, and most people won't even realize it's an aftermarket part until you hit the brakes. It's clean, subtle, and classy.
Smoked and Stealth Looks
If you're going for a "murdered out" look or just have a darker paint color like Asphalt or Raven, a smoked lens looks incredible. When the car is off, the light basically disappears into the black trim of the rear bumper. But when you hit the brakes, the LEDs punch right through the dark tint. Just a heads up though—check your local laws. Some places are a bit picky about smoked lenses, even if the LEDs are super bright.
The V-Style and Sequential Options
This is where things get fancy. Some lights have a "V" or "T" shaped LED bar that stays on as a running light, and then a separate cluster for the brake light. Some even have integrated reverse lights that are way brighter than the weak factory bulbs. If you've already upgraded to Valenti or Buddy Club tail lights, you'll probably want to find a 4th brake light that matches that specific LED signature.
The Install: It's Easier Than You Think
Don't let the wiring scare you off. Installing an frs 4th brake light is a solid Saturday morning project that shouldn't take more than an hour or two, even if you're taking your time.
The hardest part is usually just getting the car high enough to work comfortably. You don't necessarily need to take the whole bumper off, though some people find it easier. If you have a set of ramps or a jack and some stands, you can usually reach everything from underneath.
You'll be dealing with a few 10mm bolts and some of those annoying plastic trim clips. Be careful with those clips—they love to snap if they're old and brittle. If you're doing this in the winter, try to do it in a heated garage so the plastic doesn't get too cranky.
Wiring: To Solder or Not to Solder?
This is where people get stuck. Most 4th brake lights come with three or four wires: one for the ground, one for the running light (parking light), one for the brake light, and sometimes one for the reverse light.
Plug-and-Play Harnesses
If you hate the idea of cutting into your factory wiring, do yourself a favor and buy a PNP (Plug-and-Play) harness. It's a small jumper that goes between your factory tail light plug and the car's wiring harness. It gives you easy tap-off points for your new light. It's worth the extra twenty bucks just for the peace of mind and the ability to return the car to stock easily if you ever sell it.
T-Taps and Splicing
If you're comfortable with a pair of wire strippers, you can just tap into the existing lines. Usually, you'll tap into the driver-side tail light wiring. Just make sure you use decent connectors. Avoid those cheap "vampire" clips if you can—they tend to vibrate loose over time or cause corrosion. Heat-shrink butt connectors or a quick solder job with some electrical tape is the way to go for a permanent, weather-proof connection.
Dealing with the "F1" Flash Feature
A lot of these lights come with a strobe feature. Usually, there's a specific wire or a switch on the back of the light that toggles this. If you want the light to blink three times before staying solid, you'll need to make sure that feature is activated.
Personally, I love the F1 flash. It gives the FRS a bit of a race car vibe. However, if you find it annoying or if you're worried about getting pulled over, most units allow you to set it to a standard "solid-on" mode. It's nice to have the choice.
Common Issues and How to Fix Them
Sometimes after an install, things aren't quite right. The most common issue is the light not coming on at all. Nine times out of ten, it's a bad ground. Make sure your ground wire is touching clean, unpainted metal. If you've tapped into a bolt on the chassis, maybe sand off a tiny bit of paint to ensure a good connection.
Another thing to watch out for is condensation. Since this light sits low on the bumper, it takes a lot of abuse from rain and road spray. If you buy a cheaper unit off eBay, it might not be sealed perfectly. A lot of guys like to run a thin bead of clear silicone around the seam of the housing before installing it. It's a bit of extra work, but it beats having a foggy light two months down the line.
Final Thoughts on the Upgrade
Adding an frs 4th brake light is honestly one of the most satisfying "little" things you can do for your car. It's not going to make you faster around a track, and it's not going to give you more horsepower, but it makes the car look right.
It's about finishing the design that Toyota and Subaru started. Whether you go for a smoked-out look or a bright red F1 style, it's a great way to make your FRS stand out in a sea of stock cars. Just take your time with the wiring, make sure everything is tucked away neatly so nothing snags on the road, and enjoy the new look. Every time you lock your car and see those lights flash, or see the reflection in a storefront window, you'll be glad you did it.