After being told that our 1974 Valiant's tail-lights were barely visible in the rain, we invested $17 at the local AutoZone for a pair of "super-bright" LED replacement bulbs, size 1157R (to replace size 1157 incandescent bulbs). You can see the promises on the new bulb packet, and we decided to test them out.
Now, let's see how it actually works. The fit was perfect and easy. We put one into the right hand socket, and one into the left. The LED bulb is not nearly as bright; even at its brightest point, it doesn't really seem to match the light output of the standard bulb. Looking at it head on, one could make the argument that perhaps it would be a little brighter in the center inch, but from any angle that advantage disappeared completely. However, the LED had a major advantage over the conventional bulb: it lit instantly, and seemingly a half-second before the standard bulb. There was a very, very clear difference in reaction time which could be important in real life.
The photo above shows the standard bulb on the left - a 1974 bulb, we presume - and the LED on the right.
The same effect occurred with tail-lights (above). Note that with standard "my headlights are on, I'm over here" use, the LED bulbs do indeed see brighter.
Now, we see our aged, standard bulb on the left - quite possibly the one the factory put in - and a new bulb on the right. It seemed ever so slightly brighter.
Our conclusion: don't waste your money on the $17 AutoZone bulbs. Instead, if you need brighter tail-lights or brake lights, get something higher quality; and if you need better brake lights and have a car before those pernicious third brake lights appeared, get an LED third brake light. Mopar Action recently tested LED lights and ended up with a custom solution; we'd like to refer you to that in their back issues department (April 2006).
For sale: one pair Super-Bright LED 1157R bulbs, barely used.
After posting this article, we were contacted by lighting specialist Daniel Stern, also a known slant six enthusiast; he was a primary resource for Rick Ehrenberg's Mopar Action articles. We are not Ehrenbergs, though, and needed something easier. Dan made the following suggestions for tail-lights:
1) Use an LED third brake light (read about it!)
2) Rewire the bulbs so that the brake light would not double as the turn signal; instead, the turn signals would be shared with the backup lights, which would move to amber bulbs. The down-side is, of course, amber backup lights. The up-side is that research shows that combination brake / turn signals are less effective; and this modification also makes installing the LED third brake light easier. We did it the other way: we did the third brake light first, because it was the least intrusive and time-consuming and most important, and we'll do this rewiring trick later. It does make sense to only do it for cars that do not get state-inspected, I can easily see a failure there.
3) Use a better bulb. He sent along, for demonstration purposes, four sidelight bulbs, which were visibly brighter than their predecessors; and a pair of new brake light / turn signal bulbs. These tested out as being more powerful than the originals (or our brand new conventional replacement bulb) to the tune of around one f/stop on our light meter. The difference is pretty visible in the photos, too, first in the tail lights...
...but also in the brake lights:
Dan claims the P3496 lamps are 40% brighter, and we can't argue. We don't even have to tell you which is original, and which is new. (Oh, and they don't really look orange; the camera couldn't deal with the spectrum properly.) The new side marker lamps, 2886x, are 60% brighter, according to Dan.
There are ways to install good LED panels into older cars, but it involves either getting multiple-LED panels designed for this purpose and cutting them to fit the shape, not something for the faint of heart; or being lucky enough to find a panel designed specifically for your car, which could work for people with particularly popular muscle cars, but will leave most of us out in the cold (and is likely to be a pricey solution.)
Resources: Daniel Stern Lighting, Mopar Action
Find out how we installed an LED third brake light, and whether it was worth the time and trouble!
Still to do: convert front side marker lamps to blink with the turn signals, and switch to amber turn signals in back.
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