Thanks - I have one gun that has a light on it, and it goes on and off fine, but all other weapons with no light attached the F key doesn't do anything.
I've had a light on one gun and have used it fine, but now on other weapons or items the light won't turn on.
Having a helmet light does not turn on when using weapons or items that not equipped with a light or other light producing items isn't a bug... Sorry I don't get that. It worked fine till I swapped out for an undamaged higher level one.