How can I tell what voltage an LED is?

[BatteryCharger]

On my truck there is a really bright LED that lights up on the fuel gauge when I am low on fuel. It is an ugly amber LED and I would like to change it to a blue one. How do I know what voltage it is operating at? Is it possible that it's running from the full 12v of the electrical system? Measuring the voltage when it is on really isn't an option, it would be much too difficult. What do you guys suggest I do?

Thanks /ubbthreads/images/graemlins/smile.gif

 

[WildRice]

It is most likely a 1.7v LED. If it is powered from the CPU at 12v and resistored internal to the CPU, you should be able to just swap out the LED itself. They do make 12V LED's, with an internal resistor, but I am sure that your amber one IS NOT one of these. If you just swap out the LED itself, it will be underdriven, but much more visible then the yellow one.
Jeff

 

[Burnt_Retinas]

Ditto WildRIce,

Simple and cheap is the auto guy's thinking. It'll just be resistored from a higher voltage, not necessarily 12V though. Throw in a blue and it'll almost be guaranteed to work. Even 5V from a CPU will light a blue LED with resistance. Make sure the polarity is correct though or it won't light up. If it doesn't light up, turn the LED around. Being a blue LED it may be a bit bright at night though. All blue's seem to be very bright.

Chris