How many resistors for led bulbs

[bentprop]

How many resistors do I need for an 03 led tail light bulbs install or does the circuit board negate even using them?

 

[LoneWolf3574]

Many come with resistors in them already, a simple search on Amazon usually finds what you need. Regardless, it's not a matter of how many but how much resistance, and most on Amazon are 6 Ohms.

 

[tron67j]

I usually reach out to one of the electrical engineering team in my family for this, but they are out. I think you calculate the resistance by: R = (Vin - Vf)/If where R is the resistance you need, Vin is the DC input voltage, Vf is the forward voltage drop of the LED (should be specified in the datasheet) and If is the current required by the LED (also should be in the datasheet). Hopefully some much more knowledgeable than me can QA my answer. If I get an update from family will post again.

FYI I had this formula, but I found a much better explanation which I copied from another webpage.

 

[Smokeybear01]

6 watt 50 ohm resistors-you'll need 4 just for the rear (2 each side) and 2 more for the front turn signals. It's a simple job but definitely mount the resistors on a metal surface because they will get hot when in use. I'll attach a couple pics to show what I did.

 

[Smokeybear01]

You won't need resistors for the backup lights, license plate light, or fog lights. Do buy headlights that are already made with the compliance internal or you will go through a lot of resistors if you drive much at night. My entire truck inside and out is now lit up by LEDs. Running lights and everything. They look and work so much better than old school.