98-02 Accord Coupe Cluster Colour Change....

[hughezee]

On 21/12/2016 at 0:10 PM, Laird_Scooby said:

The heat from the OE filament bulbs can cause the bleaching effect

Totally agree if it's a direct swap buddy, but when I have put LED's in place of bulbs I will fit a resistor and never had bleach happen and no premature LED failures - basically a 1/4 watt resistor that controls current through the LED. 470 ohms is typical for 12V but that value can vary based on the voltage drop of the LED and the current rating.

[Laird_Scooby]

All the ones i linked to are direct swaps Stu. When i've fitted a "special" LED as in one i couldn't buy off the shelf i've always used a 680 ohm resistor to keep the current down to 20mA or thereabouts. Bear in mind most LEDs have an Imax (maximum current) of 30mA, Vf (Forward Voltage) of 2.2V typically for red, yellow and green and 3.6V for blue and white and most alternator voltage regulators are 14.4V, a 470R resistor will usually give a forward current of about 26mA :

(Vcc - Vf)/R = (14.4 - 2.2)/470 = 12.2/470 = 0.02595A or a smidge under 26mA

Not quite so bad with the blue and white ones that have a Vf of 3.6V :

(14.4 - 3.6)/470 = 10.8/470 = 22.97mA

Do the same sums with a 680R and you get much lower current in the LED but still good illumination :

12.2/680 = 17.94mA for the red, green etc

10.8/680 = 15.88mA for the blue.

Ideally for the longevity of the LED you need to run them at 20mA or less, you won't in practice appreciably notice any less output until you get down to about 4-5mA but even then it will still be reasonably bright.

As you rightly stated though, on a 12V supply a 470R resistor is about right - the anomaly here is that the alternator is 14.4V output so that's what you need to work on.