I've kind of been wanting to upgrade my CHMBL (aka 3rd brake light) to LED, but hadn't been impressed by most of the usual options.
- I was not impressed by any of the 921 LED bulb replacements available. The reflector design lends itself to lopsided/directional lighting if using a non-incandescent bulb.
- The off-the-shelf options currently available seemed ridiculously priced considering how inexpensive the components used to make them are.
- I thought about building my own LED array on a panel or circuit board, but decided that it wasn't worth my time, effort, and the cost of gathering up all the needed supplies.
Then I had another idea; all I really needed to do was find a small universal LED strip that would be suitable as a brake light and also small enough to fit into the housing. After trolling through the Grote and Trucklite catalogs and all the cheap (though sometimes expensive) crap from China on eBay and Amazon, I began to get discouraged. Luckily, I stumbled upon a promising candidate at Summit Racing: http://www.summitracing.com/parts/upd-39687b/overview/
The part arrived today and I am happy to report that it's just about perfect for retrofitting the NA (and probably the NB?) 3rd brake light! The strip is a 3-wire design with a dim (taillight) and bright (stoplight) setting. The dim setting is probably on par with the stock 921 bulb, the bright setting is substantially brighter. It fits easily inside the housing, and in fact you could probably stack two of them in there if you wanted to get really crazy. Two lights would definitely be overkill though, and might be a potential safety hazard if wired up to use the bright setting. It would definitely look cleaner and be easier to keep things more secure (because you could tape or glue one strip on top of the other, and then tape the top and bottom to the lens) with two of them though. I keep thinking that it would be cool to make a "version 2.0" with two strips and wire up a limit switch on the brake pedal so that it uses the dim setting on normal braking and then steps up to the bright setting on hard braking. I really like that idea, but it also seems like more work than I care to do at the moment.
I played with a handful of ways to mount the strip inside the housing, and ultimately decided that 1/8" to 3/16" from the bottom and mounted parallel to the lens yielded the cleanest view when illuminated. When centered vertically, most of the light appears to come from the top half of the lens because of the refractive lens and the angle from which it is usually viewed (looking slightly downward). When mounted toward the bottom half of the housing, it illuminates the lens quite evenly from most angles.
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I used a couple of rubber bumpers to space it from the bottom of the light, and to keep it in place I glued it with some clear silicone adhesive and a couple dabs of super-weatherstrip adhesive on the lower corners. Then I drilled a couple of holes and put two screws in to help secure it even more. Looking back in hindsight, I should have just used some thick 3m double-sided tape. It would have been way quicker, easier, and cleaner.
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I might pick up some 194 bulb wiring adapters (like these found on ebay) so that I can plug it directly into the stock harness and keep it very tidy.
I've attached some pics of the light and how I mounted it, but no "action shots" yet as I'm waiting for the glue to cure before I put it on the car.
TLDR?
1. Buy this light http://www.summitracing.com/parts/upd-39687b/overview/
2. Tape, glue, or screw it to inside of stock 3rd brake light housing
3. Hook up the red (+) and white (-) wires
4. Reassemble and reinstall
5. Laugh at all the suckers who pay $40-$80 for LED 3rd brake lights