Sunday, November 30, 2008

LEDs are cool.

I’ve been working on my engine bay as funding and time allows. One of the first updates that I did in this area was to modernize the engine bay's light, to an LED. You all know by now the advantages of LEDs (lower current drain, less heat), but I thought it would be interesting to document here the actual temperature differences.

For these tests, I popped the lens/cover out form the housing, and began readings with the current LED that I am running. First I took an ambient temperature reading. (The instrumentation used is an EXTECH multimeter, with an IR Temperature sensor.) The first picture below shows an 81F (27C) ambient temperature.

Energize! This next picture is the temperature reading on the same spot, of the LED light, as you can see there is no measurable temperature rise. Perhaps over time it may go up a degree or so, but it never feels much if any, warmer than ambient.

Next up is our old friend the incandescent bulb. The temperature began to rise quickly, I snapped this first picture at 231F (111C)…

...and I stopped after this picture, at 278F (137C):

After a brief cool down, the bulb was literally too hot to handle.

...which is about where it stabilizes at, which is nearly 200F (110C) above ambient with the lens cover off! Imagine opening the engine bay and activating this light, on a warmer day, and with a warmed up engine bay, and it is understandable how those added degrees could contribute to a 27 year old plastic housing meltdown. : (

So, as shown, it’s no surprise that every now and then we see or hear of a melted engine bay light housing. It's one of those "factory quirks" our cars have. Oh, and by the way, the internal cabin dome lights (above rear view mirror, and on rear shelf) are made to have the same incandscent bulb, housed in ...another plastic housing.

So this is a simple fix, go to your favorite vendor and order an LED replacement light kit.
DMCH (or your local DMC facility) have them for $1.99 each (#SP11305).

The one that I have pictured is not a DMCH product, it is from Specifically, these are their Festoon bulbs (4210-WHP6)

Picture from:

They're relatively expensive at $15 per bulb, but what is neat about these is that not only are they bright, consume less power, run cooler, but they also carry them in a “warm white” option. This is different from the typical LEDs that have a blue-ish hue to them. The “warm white” options tries to duplicate the warm, light yellowish, color of an incandescent bulb – and it’s pretty close (I used their equivalent “warm whites” on my dash, and I really liked how that turned out). This color option is closer to the look of an 80's car, where as the typical blue-ish LEDs seem (to me), not in line with the car's vintage.

It’s tough to capture in pictures, but the first picture above is the best shot, in the dark, in an attempt to capture both the illumination and color of this bulb. Had I used the “cool white” you would have seen a bluish tint on the picture.

Unlike the incandescent version, these are directional, that is they only illuminate on one side, and per their spec, on a 120 degree light arc. I haven't found this to be a problem, and again you can reference the picture above to see the result.

Oh ... and if you do order them through, don't use this bulb on the interior, it is much too bright for that application.

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