I plan on installing a set of 4 of the same door courtesy lights around the floor areas for extra convenience. I want them to only illuminate when the doors are open (this part I can figure out) but I want them to illuminate and dim out like the dome light does (this part I can't figure out).

I also don't want to just tap into and draw from the dome's power source, so I know a relay will come into play here. Advice? What's the right way to do this w/o any overloads on the fuses? Thx

 

as a reminder, relays are on/off, not high-low/off; a relay won't help any, probably won't be any use at all.

in order to dim, you will need some source of dimming, whether it's the dome light power, or another auto-dimming circuit.

 

Tap into dome light power and use bigger fuse.

 

Great, I was afraid of that. So what's the safest way to tap into that dimming circuit?

 

I thought about that, but are those wires strong enough to support that kind of current? We're talking 4 extra incandescent bulbs... Anyone else's opinion on this strategy of using the dome power and increasing the fuse load?

 

my concern is less the wire (although it is a concern), but more on the controller.
if it handle the load, you will need an alternate option.

 

Engineer's approach, there one way to find out: blue smoke or no blue smoke, at least you learn something.

By the way hooking a device in parallel is a current divider. You might want to duplicate the circuit at its power source.

 

all LED's no matter what they are the best

 

They sell LED bulbs that fit any socket nowadays. They are generally not as bright but will use less than a third a current of an incandescent bulb. And if I'm not mistaken they also make dimmable LEDs.

 

Wire a decent sized capacitor to one courtesy light in parallel with the bulb or LED, when your door switch (ground trigger) is shut off, the cap will act as a dying battery creating a dimming effect on all 4 courtesy lights.

I made a video to demonstrate. Use a heftier capacitor. I used a small 25v 100uf for this single LED and it dims pretty quickly. Do some trial and error.

 

i added a few leds

IF you have an aftermarket alarm with dome\courtesy light support
they will turn on when you hit the KEY FOB