Well now that I actually have the time, I have taken apart my dash again in the quest to eliminate ugly green lighting So the temp control unit is out and disassembled, but I need some help with voltages and the like. So I have a picture of everything here: http://greginfinity.tripod.com/led/ The red and blue arrows point to locations that normally have lamps and I want to replace them with LEDs. The problem is that I just burned out a 5v LED here. So I am wondering if anyone knows the voltage here... I know I could use a voltmeter but I don't have one.. yet! I would also like to know the voltage that runs across the LEDs where the yellow arrow points. This is the array of lights that illuminate when you press a different fan location. One last helpful piece of information would be to refresh my memory on some physics. If the voltage where the blue/red arrows point to is 12v, and the LEDs are 5v, then the resistor*current should ve 7v? So I forget how current and resistor rating relate, and how would I find the current? Thanks for all the help guys. Hopefully this is a success and I can do a writeup for you!

[EDIT]: Now the link works... nevermind the interesting info on the page....

 

Ok, here is what I did. When I was in the process of changing out all of my green and orange LEDs to blue in my 96’ manual a/c module, I thought about changing out those little bulbs to blue LEDs. What I did was take out the little bulbs and put in blue LEDs where the existing bulbs came from. Then, I pulled out the voltmeter and I located a constant 5v source on the a/c circuit board and tapped a mini-wire into that. Then I led that wire to the three little LEDs that I put in and then led a ground wire to all three LEDs. I plugged the a/c board in and everything worked. But here is the catch. I could not find a 5v source that only came on with the lights. So this meant that the LEDs would constantly be on, if I liked it or not. Also, the spread pattern of the bulbs was not very large like the regular bulbs. So, different areas of the a/c unit where the LEDs were located were brighter than the areas that didn’t have a LED directly behind it. But I did successfully change out the green and orange a/c LEDs to blue, so it now matches my intelliglo needles and reverse indiglo gauges. Also, the LEDs match my true blue window switches that use the LEDs I got from RadioShack.com that are a solid blue. So until I find a LED with a larger spread pattern, I am gonna use the stock regular bulbs in the a/c module.

But regarding how to wire in a resistor, as far as I know, all you need to do is find a 12v resistor that regulates 7v, which means it is pumping out 5v on the “out” side. It should work, just go to a Radio Shack and ask them what they think. Maybe someone here might know a little more. Just tinker around with it. I purchased a spare one from a junk yard and totally tore it apart figuring out ways to do different things with it. All in all, it was pretty fun putting in those blue LEDs. Good luck guy.

 

Thank you vey much for the information, it is most helpful. I was indeed worried that a blue LED might not have the same spread as the bulbs, but I am going to try a wide angle LED and see if that makes a difference. One other handy thing I discovered that people might want to know is that LEDs can be shaved down to fit in tighter spots. I.E. you don't have to find the correct matching size, you can just take the LED to a bench grinder and shape it. But try to keep it minimal since it does affect the light pattern coming out and if you go too far, you will mess up the diodes. I guess I will have to go to the shack today and pick up some goodies. Thanks again

 

A standard LED will pop immeiately when connected to a car battery because the voltage is too high, but also the available current is too high compared to the current handling capability of the LED compared to the resistance across the LED's legs.

Easiest way is to put a 1K Ohm resistor inline with the LED and it will reduce the voltage and current down to acceptable level. Or you could get a 10k POT (variable resistor) inline with the LED, set it to it's highest setting and then connect to the 12v. Adjust the POT down and the LED will get brighter. You know you're overpowering the LED when a red LED goes orange, or a Green LED goes yellow - you need to adjust the resistance back up. When you get the level you want, measure the resistance across the POT terminals you used. That's the resistance you need in a resistor to get the brightness you want.

Also remember that when you have the engine running the voltage is 14.5v+, not 12v, so if you plan your circuit under 12v and put it in a running car then you risk overpowering the LED and burning it out.

 

BOOYA! well the battlestation is now fully armed and operational. I ended up with a 270ohm resistor in line with the LEDs after doing a little mental math. Hopefully I will be able to get some night pics so you can see the setup. All the ambient lights are blue and when you switch on the different levels of the vents, you get a red light underneath. Ramius is correct in the fact that the LEDs dont have a good spread for the ambient lighting however, so I will need to figure out a better way. This is an inexpensive and fun mod for those that like to take things apart. The writeup will be on the way as soon as I figure out a good way to illuminate the buttons. Thanks for all the help guys!