Wednesday, December 8, 2010

Red trunk lights on the cheap

I've been embarrassed at star parties by the bright white light trunk light in our Taurus. I've finally done something about it, in my usual cheap way. I made a red LED light. I drilled four holes in a 40mm long 3/8" thick wooden dowel. I stuck three mini red LEDs into the holes, with neighboring LED leads going into the same hole. The last hole on one side also got a lead from a 330 ohm resistor (the values will differ depending on your LED specs and battery voltage). I twisted the leads together for better connections, cut them shorter as needed, taped it all up with electrical tape (OK, I've left out some missteps), and popped it in in place of the trunk's tubular incandescent 12V bulb, in such a way that the unconnected LED lead on one side and the unconnected resistor lead, made contact with the metal contacts. Works just fine. Rather dim in daytime, and I haven't tried it at night time. The old bulb drew 0.7A. The new LED system draws much, much less. So no danger of running out the car battery if I leave it on overnight.

I still need to do this to the dome light. My reading of Texas law suggests that alas I am not allowed to do this for the puddle lights ("running board courtesy lights" must be amber or white--maybe this only applies if they're on while the car is going, but why take risks?), so when I go observing, I'll just put some tape over them.

The cost for the whole project was low.  I had the 330 ohm resistors lying around for years (I think they're 1/4W;  ideally, I should have used 390 ohm).  I got the LEDs for about two cents a piece from Tayda Electronics.

There was one unexpected cost.  I blew a fuse when removing the original bulb.  Lesson: Keep the fuse disconnected when doing this, except when measuring stuff.


  1. Oh, so, you're the one with the bright trunk. :)-

    Hopefully, your solution will work. Though, I was also thinking that you could place red duct tape over the trunk light. I don't know how well it would work. I also have no clue if it's legal or not.

    Another idea: after arriving at the star party you can simply take out the fuse for the inside lights. When you're ready to leave you can put the fuse back in.

  2. The LEDs were too dim, so I got brighter ones and installed them today.