I have some 4 volt LED's that I wanna install inside my climate control unit. Will I still need to use a resistor if I hook 3 of them in series, since the total voltage would be 12 volts? Trying to find the easiest way to do this.

It depends on what the specs are on them, I have a bunch of LEDs that can handle between ~2.4-3.5 volts. So I always run them in series of 4.

Edit: I reread your post, if they can take 4 volts, you don't need a resistor, but remember, car electrical voltage fluctuates, It can get down to 10 volts, *I think* before it won't start, and can be as high as 13+ if the car is running with no load on the alternator.

This post has been edited by Cutrara: Dec 23, 2005 - 12:20 PM

my celicas alternator spikes way up at 14v when i messured from the dome light socket. but the climate control stayed damn near 12v, in both battery and altenator.