I'm currently downloading so haven't seen for myself yet. If the machines do have a light on when they're unpowered though, that's be pretty unrealistic and immersion breaking... I really hope they don't...

They don't.

Thanks for letting me know. :)

I still didn't actually know because up until an hour ago I was using the "Afraid of the Dark" mod, expecting to be able to make a bunch of neat new light items down the line. Honestly didn't expect a huge bubble of light to follow me about for now apparent reason...