uniseriate

The third brake light on my hatchback was becoming very dim with age. I took a look at the bulb and found that it was internally scorched with particles from the filament. I decided to replace it with a more visible and reliable LED unit. LEDs also light up faster than filament bulbs. It is only a difference measured in milliseconds but on the highway that difference could lead to an extra 20-30 feet if the other driver is paying attention.

LED replacement "bulbs" that you can find on eBay do not work very well. LEDs are a point source of light and cannot reproduce the 360 degree viewing angle of filaments. It is best to use a unit that has the LEDs facing rearward rather than trying to use a reflector meant for a filament based bulb. Additionally, the bulbs on eBay often do not have any current regulation, which leads to a short life. I opted instead for a complete unit that I could retrofit in the Civic housing. After scouring eBay, I came across an auction for a LED CHMSL out of a second generation Prius for pretty cheap. It was roughly the same size as the one in the Civic so it was a good candidate.

The Prius CHMSL turned out to be a sonically sealed unit. I used a dremel to carefully cut around the lens to separate the circuit board inside. Once out, I studied the circuit of the CHMSL. It was equipped with a diode, varistor, and three banks of resistors to regulate the voltage to the three banks of LEDs. This circuitry allows the LEDs to deal with the voltage fluctuations that occur in automotive electrical systems. I found twelve LEDs in the CHMSL arranged in series-parallel circuit. There were three banks connected in parallel with each bank composing of four LEDs wired in series.

I took out the Civic's CHMSL and found that it was also sonically sealed. I had to use the dremel around the lens in short cuts to prevent the plastic from melting and causing a mess. After leaving plastic particles everywhere (wear eye protection!), the outer lens was finally free. Inside, there was a Fresnel lens that covered the inner bulb area. It was easy to remove as two screws on each side fastened it to the housing.

During the test fit, I found that the Prius CHMSL PCB was slightly too long. It was hitting one of the plastic mounting posts for the Fresnel lens. Cutting off one of the LEDs solved the issue. As a side benefit, the shortened PCB could now be fit with one of the LEDs centered directly beneath the focal point of the Fresnel lens.

After that, it was simply a matter of attaching the PCB to the housing. I removed the metal reflector in the housing for more room and to prevent any component from shorting out against it. A quick dab of JB Kwik on both sides of the PCB is enough to hold it.



JB Kwik was also used in reattaching the two halves of Civic CHMSL. During this step it is important to hold the lens near a light to make sure that there are no spaces between the halves. Dab up any errant spaces and the CHMSL is about as waterproof as it was before.

The final step here is optional but I did not want to hack up the stock bulb holder in case that I had to revert back to an original CHMSL. I took the now useless bulb that was originally in the Civic CHMSL and used a dremel to cut it in half. I then carefully soldered the leads from the bulb to the leads from the modified LED CHMSL. After it cooled, I filled the bulb base with JB Kwik. JB Kwik is not conductive and so it makes a good electrical insulator. It is also decently strong and so the modified will not crack upon installation. If you prefer not to DIY, you can also find plastic T10 bulb bases from various LED sites online for pretty cheap.

Everything worked well and so I'll let the pictures speak for themselves.



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elusivEm1

that actually looks good

1slo4dr

hey im having a problem getting the lens out ... i got the plastic cover from the bottom of the spoiler but the lens wont pop out. . any help would be great thanks !