LEDs for the Rear Lights

Post by **kelvin6** » 05 Jul 2005, 21:24

Convert all my rear lights (except the rear fog) to LEDs?

Originally I had this idea for my old car, but that car got totaled before I had the chance to experiment. My only concerns of installing these LEDs for the brake lights, is how visible would they be during the day time? I'm sure some of you have seen 'Matrix' bulbs that have like 24 LEDs facing forward and about 6 or 12 facing to the side to illuminate the reflectors. I know at night they are quite effective. Now that I think about that, I probably should try it out on the center brake light to see the results, before doing all of them. Unfortunatly there are no bulbs that are DOT approved for this application.

Turn signals are more interesting debate, it might be better to keep them as bulbs. With LEDs you get speed when it comes to lighting up the bulb, but is it necessary for the turn signal to have a dwell time for illumination, because the dwell time provides a longer time for others to see the light?

Some input would be nice.

White850Turbo · Post by **White850Turbo** » 06 Jul 2005, 09:11

You'll need to do some wiring in of resistors to get it to work right. The LED bulbs use much less wattage than the standard type bulb and will therefore trip the "faulty bulb" idiot light on the dash. As for the blinker lights, the wattage level is directly related to the frequency of the lights flashing. You'll need to experiment with resistors on those circuits as well to get the flash rate close to stock.

I am using OEM bulbs for the brake lights under the philosophy of "Why fix something that isn't broken?". I've noticed however that the amber film on the OEM blinker bulbs tends to flake off after a period of time, resulting in more of a white output rather than the typical orange. I've replaced them with the pearlescent Sylvania silverstar 1157 type bulbs. They look really cool in the front and seem to light up even brighter than the OEM bulbs, with no film flaking.

Post by **matthew1** » 06 Jul 2005, 10:48

White850Turbo wrote:I've noticed however that the amber film on the OEM blinker bulbs tends to flake off after a period of time, resulting in more of a white output rather than the typical orange.

Agreed. Mine and nearly every 850's I see are near white. Grabs more attention from drivers behind you because it's "different"? Who knows.

Post by **kelvin6** » 06 Jul 2005, 21:42

Wiring is no problem, put a 3 ohm resistor PARALLEL with the LED, the 3 ohm resistor will simulate a bulb (I just checked this). There is a minor disadvantage, if the LED died, the indicator light for a faulty bulb will not come on, because the 3 ohm resistor is tricking the system to believe a bulb is there, LED or no LED.

I'm going to try this on the center brake light. Worth investigating.

frootmig · Post by **frootmig** » 28 Aug 2005, 15:48

Hi Kelvin,

I would re-think the value of your resistor, a 3 Ohm resistor will draw a current of 4 amps and will dissipate a power of about 50 watts (lots of heat generated).

You will need quite a few LED in parallel to give the same brightness as a 21Watt filament bulb, the light is also quite directional, so you will need to spread the LED's out over the surface of the lamp casing to give the same effect.

Frootmig