How-To: LED Third Brake Light

[1997ThunderbirdLXV6]

We've all seen melted brake light housings and blackened light bulbs. Even with 912s, that keeps happening; meanwhile the brake light is dim.

Going to LED seems like a no-brainer, but there are various options. I did experiment with LED bulbs, but I didn't get the look and brightness I was looking for.

After playing with a few units at the junkyard, I settled for a Buick Lucerne brake light, which includes six upward shining LEDs, a complex reflector, and a clear lense. Price at the junkyard: $11.

Step 1
Obtain Buick Lucerne third brake light. Here is how to remove it from the car:

Step 2
Trim the unit. This is the great part: only minor cutting on each side is required, and the unit fits perfectly into the housing. It even clicks into place on top of the existing clips. (Ignore the beige leatherette on the second picture; that was a first attempt.)

I removed that leatherette and replaced it with a black foam sheet wrapped around a wood stick at the trailing edge for a nice round shape:

Step 3
Trim the old assembly. You only need the bottom portion, i.e., the part that screws to the shelf and clips to the housing. You also have to cut out an opening for the connector (which faces down).

Step 4
Cut off the old bulb sockets and attach the GM connector to the harness.

Step 5
Install the unit. You won't be able to screw it in. Instead, push a small zip tie through the hole from above, then secure with another zip tie end from the trunk.

Step 6
Assuming you have LEDs in the corners, as well, cruise control won't work at this point. You'll have to wire a bulb or resistor into the circuit. Caution: this may get hot, so choose a location accordingly. As always, follow these steps at your own risk; I'm not a professional!

Enjoy your new third brake light with a factory-ish look and excellent brightness:

 

[1997ThunderbirdLXV6]

 

[Torque]

Looks good. I had decided quite a while ago to try a different approach and already bought components, but yours looks like a good solution for people who can find the Lucerne assembly for a decent price. The typical price for used ones on eBay is $60.

I had tried several aftermarket LED strip types, but like you, I wasn't satisfied with the brightness nor appearance. Just a waste of money that was, cuz I doubt I'll ever find a use for them.

What I ended up with is a couple of high-intensity 921 equivalent red LEDs (10 surround elements per bulb) so that I can use the OEM assembly, and a sheet of fluorescent tube diffuser lens. I did a quick test of the LEDs shining through the diffuser and it seems to spread them out well, and they are very bright. I would have to look up the supplier docs again, as I don't recall the lumens offhand, but I seem to recall they are close to or above 921 spec. I sourced them from AliExpress, and they were only a few bucks each. No idea how long they will last; I left them on for a good bit during my tests w/o issue, but who knows.

My OEM red lens is fried, bubbled up by the incandescent bulb heat and the diffusion effect is trashed, so I don't mind hacking on it. The socket retainers are somewhat melted as well, but they still keep the sockets in place. I may mod those a bit as well. Those whose OEM lens is in good shape can just drop in a pair of these LEDs and it will look pretty close to OEM.

I'll post up my mod once done.

 

[1997ThunderbirdLXV6]

@Torque
That sounds like a good solution. My factory red lense was also melted/cracked.

Lucerne units are abundant at the junkyards in my area, and they're about $10. But when you buy online, you're really paying for the seller's time (though $60 seems a bit high).

The advantage with the Lucerne unit is that it's a DOT compliant design with brightness perfectly matching other stock brake lights.