Our Plymouth 1974 Valiant’s tail-lights were barely visible in the rain, so we spent $17 at AutoZone for a pair of “super-bright” LED replacement bulbs. You can see the promises on the new bulb packet.
The fit was perfect and easy, but that’s where the good news ends. The LED bulb was not nearly as bright; even at its brightest point, it doesn’t 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. The LED just had one advantage over the old bulb: it lit instantly, with a 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. It’s no better in person, though a bit less orange.
The same effect occurred with tail-lights (above); here, the LED bulbs do indeed see brighter.
Now, we see our aged, standard bulb on the left (probably the factory bulb) and a new, standard $1 bulb on the right. It seemed ever so slightly brighter.
After seeing the results, lighting specialist Daniel Stern 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.
3) Use a better bulb. He sent four conventional 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, 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 (one side is the standard bulb, the other is the P3496)...
...but also in the brake lights:
Dan claims the P3496 lamps are 40% brighter. 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, such as cutting multiple-LED panels to fit the shape, or getting a panel designed specifically for your car. Some companies are starting to do decent LED drop-in replacements, but you’ll still need to be careful; even the majors put out some ribbish.
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!
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