All LED's are dimmable... but you can't use just any dimmer. The secret is to install what's called a Pulse Width Modulator. This simply turns on/off the LED extremely fast - so fast the human eye can't catch it. To make an LED appear Dimmer, you simply increase the duration the LED is off in relation to the time it's on. To make it brighter, you decrease the off time duration.
To know if most any LED is already being used with a PWM, simply have the led be the main light source and look at anything that is moving quickly. A fan for example - it'll look like the blades are standing still or that they are very jerky in their motion. Often, you can do it simply by opening your hand (fingers apart) and shaking them back and forth - if they look to be moving jerky style (like watching an old time movie where the frame rates weren't as high), then you are looking at them with a PWM'd led light source.
That being said, I'll see if I can find a couple links for dimmers. Be right back.
I have experience with this one. I installed it in my slight to dim the lights over the dining table. I had to pull a ground wire to the 3 LED's. I'm not certain, but I THINK, had I ran the other output wire that's meant to go to the ground wire of each light to the chassis ground itself instead of to the lights directly, it would of still worked.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
This one, I saw a few youtube vids of people installing them to dim the main cabin lighting like you are wanting to do. But I've not used one myself.
https://www.amazon.com/ALOVECO-Inter...xpY2s9dHJ1ZQ==
Linear Mode
