How to DIM an LED Light?
Dimming an LED light is as easy as adding resistors to the connection or even several resistors, to ensure you get the right brightness – this is called analog dimming. In many states, there are regulations to the brightness (and colors) of LEDs on cars, which is why this is important to take note of.
You might not have as much control over the brightness as you would using pulse-width modulation (PWM). PWM means that you can encode how your LEDs will shine – brightness, color and characteristics – as well as have full control over the power supplied.
But, for the sake of convenience dimming an LED is just a matter of adding resistors, but this largely depends on how bright your LEDs are in their original state.