Very useful LED tech info for noobs

[Paul Workman]

Since many of us have or are considering converting some/all of the OE bulbs in our cars with LEDs (specifically), when I ran across these two videos I thought some might benefit in several ways: avoiding confusion and mistakes and get answers to common questions re LED conversions.

This first Youtube video explains the basic LED operation; what is and is NOT required to operate them successfully.

https://www.youtube.com/watch?v=Yo6JI_bzUzo

This second Youtube video explains HOW to adapt an LED to various power sourced without instantly burning the LED up (or sometimes causing it to literally explode!)

https://www.youtube.com/watch?v=NfcgA1axPLo

After watching these (above) videos, you now understand the key requirements of all LEDs:

• Polarity (which is the (+) and which is (-) lead)
• (Forward) voltage requirement
• Current limitation

One of the most often asked questions I got after my article on converting the headlights to LEDs was due to confusion with regard to LOAD resistors, and series resistors.

So far, so good. But, LEDs voltage and current requirements vs. stock (filament) bulbs are quite different. So, two more bits of info are necessary to successfully convert your car to LEDs.

From the second video, we learned about limiting the current, using a resistor connected to one leg of the LED. But, practically ALL LEDs sold with the intention of replacing stock (filament) bulbs in automotive apps, the VOLTAGE and CURRENT parameters are already built in - as far as the particular LED light is concerned. But, in the C4s, ALL of the stock filament bulbs controlled with the turn signalling (only), will not function without a modification to the circuit:

a resistor of a value similar to the resistance of the filament bulb being replaced must be substituted in place of that old bulb*, or

a (recommended) special "LED" flasher must be installed in place of the stock (turn signal) flasher.

*Dealing with the fog lights presents several options:

1. cutting and grounding the actuator coil leg of the fog light relay - providing the relay a ground to replace the one removed by installing the LED headlight
   
2. installing a resistor ("load resistor") in place of the stock (filament) bulb (which results in restoring the stock functionality of the fog lights that cutting and grounding in the step above creates).
   
3. a special (digital) relay can be installed to supplant the stock relay. (This method features maintaining the stock (fog light) functionality with the advantage of minimizing the stock current load AND does not require the stock wiring to be cut.