When trying to add aisle lights to my vehicle, the crafting options stays disabled and “1 flashlight (off)” in the “components required” section is still red, although I have a flashlight on me.
Can someone try if that’s reproducible?
Version: 0.E-2 build 10478 (vanilla)
I’ll give it a try, but it can be helpful if you add the version of the game and the active mods in your world to a bug report.
If you play the stable version and I try it in a random experimental version, the results might be very different.
I’ve tested it in 0.E experimental build 11076 and it seems to work fine.
Is your flashlight loaded with a battery? You probably have to (U)nload it first.
Or is it a “heavy duty” one? The game’s a bit picky on which one you can install, you’ll need a regular one…
Sorry for forgetting the version number. I am always so annoyed if people don’t mention it, and now I’m here, doing it myself 
I edited the question. Thanks for reminding!
And you were spot on! The flashlight has to be empty (unloaded, not containing any batteries), then it works like a charm.
I consider this totally my bad, as it clearly does not mention any batteries in the recipe 
Now if you excuse me, I have to enjoy my shiny (literally) humvee in a new light 