Underhood Work Light LED Replacement

Yes, I've just switched my incandescent #90 bulb to an LED.  I used an LED advertised as GRV Ba15d 1076 1142 COB 1511 LED Lights for Vehicle Boat 2.5Watt Double Contact Bayonet Base With Glass Cover from Amazon.  And while it is slightly longer than the #90 bulb it still fits under the lens nicely.

In my typical style I've done some testing to see what the difference is.  Basically I find that it is ~4x brighter than an incandescent #90.  And it does that while pulling 1/3 the current - .2a vs .6a for the incandescent.

How did I determine that?  But using my camera as a light meter and a lab power supply that kept the voltage constant.

In the pics below the incandescent bulb is on the left and the LED is on the right.  And you are highly likely to say "Wait!  The lighting looks to be roughly the same!"  Indeed it is, which is exactly the way an automagic camera works - it exposes the image for different lengths of time and/or lens openings to achieve the same picture, regardless of the amount of light.

But, when you go look at the "camera information" in the file you can see the differences.  In both of the shots below the camera held the lens opening to f3.7 and the ISO setting to 1600.  Plus, I kept the zoom to 4.5 mm and the over/under exposure option to 0.  So, other than the shutter speed they were identical shots.

To capture the image on the left, the incandescent bulb lit one, the camera held the shutter open for .6 seconds.  But to get the one on the right it held it open for only .166 seconds.  The amount of light is an inverse relationship with the shutter speed since all else was held equal.  And .6 divided by .166 is 3.6.  

Excellent! Thanks for those test and providing another option for users. I have that one saved in my cart.

Where is the temp difference after X minutes test though?
That #90 gets blistering hot in no time.

Good question.  The LED had been shining brightly for over an hour so I touched it and found it just a bit too warm to hold my finger on.  So I got the infrared thermometer and the hottest I could find was 160 degrees.

Then I lit up the incandescent and after a couple of minutes I could find 280 degrees.  And, there was no way I could touch it for any time at all w/o getting burned.

So, there's a BIG difference in temp.  Which is pretty well confirmed by the current pulled and the wattage rating.  At 14 volts and .6 amps the #90 was pulling 8.4 watts, which is close to its rating of 8 watts.  But the LED pulled .2 amps so it was pulling 2.8 watts, which again is close to its rating of 2.4 watts.  (Maybe both were rated at a bit lower voltage?)

So you might think that the LED would put out 1/3 the heat of the incandescent bulb: 8.4 divided by 2.9 = 3.0.  But it also put out more light, which is a form of energy as well and that has to be subtracted from the wattage pulled.  Given that, the LED has to be turning the current into maybe 1/4th or 1/5th as much heat as the #90 incandescent does?

Let me answer the question about heat a different way.  I left the underhood light on for over an hour and then put my hand on the lens gingerly.  To my surprise it was just barely warm.  Couldn't even have been 100 degrees.  I think we have a winner.

To me that is as much or more a benefit as the extra brightness. I left my hood open for a few hours at the show the other weekend and it was nice to not worry about the light (heat) being left on the while time.

I agree.  Here's what can happen to that lens with an incandescent bulb:

LED's are a lot more efficient!
(About 8x, in my basic comparisons with incandescent)

This is the sort of thing I like my non-contact IR thermometer for.
Quantifying, instead of "bathwater" or  "coffee"

That underhood light is definitely one I want to replace and like many, more for the heat issue than the light. Bulb burned out long ago, but have not replace it just because of the heat.

The two courtesy lights just under the dash on both sides are #89, I think. Can I ask what you guys are using in those?    

Machspeed wrote

The two courtesy lights just under the dash on both sides are #89, I think. Can I ask what you guys are using in those?

I am using these:

https://www.superbrightleds.com/moreinfo/courtesy-light-bulb/67-led-light-bulb-12-smd-led-tower-ba15s-base/3698/?year=1986&make=28&model=796&scc_id=1452

I originally had some generic ones in there that flickered a lot. Very happy with these. They look a lot better than the exposed ones also since these have the dome/cover on them.

I am using these:

https://www.superbrightleds.com/moreinfo/courtesy-light-bulb/67-led-light-bulb-12-smd-led-tower-ba15s-base/3698/?year=1986&make=28&model=796&scc_id=1452

I originally had some generic ones in there that flickered a lot. Very happy with these. They look a lot better than the exposed ones also since these have the dome/cover on them.


Thanks Scott, great website!