Do you know why LEDs work in some cars, but doesn't work in others like the newer bmw and mercedes? Do newer cars have some sort of shut down mechinism?

Works in my friend's 03 BMW 3 series and 02 Lexus IS300. Does NOT work in my 08 Mercedes E350 (will flash on and off). These are the festoon bulbs and wedge bulbs.

 

Have the '07 W211, and the 39mm rear plate-light festoon bulbs require resistors. Don't know why.

 

The newer MB units (and other cars) use a resistence feedback type system to monitor for bulb failure. LEDs use less voltage than incandesant lights even if the wattage is the same. To override (or trick) the system, splice in 5W 100ohm inline resistors which compensate the voltage differential of the LED v. incandesant bulb. Hope this helps. Scott.

 

thanks Scott. I think it is a MB thing. Most of my friends that have the newer model BMWs have no problem with it.