Did you get a good deal on it? Have you checked to see what the problem might be?

But really it probably isn’t worth messing around with unless it was less than $10. It’s pretty amazing what you can get these days for $15-$20. I bought mine long ago before I knew what a real flashlight was, I wouldn’t buy one now knowing what I know but it’ll be kind fun to try and mod mine since I have it.

You could trade it in for one of these if you don’t already have one! (real handy for working on flashlights) https://www.harborfreight.com/jumbo-helping-hands-with-led-lights-65779.html

Also this is a great thread lube, 1 tube will last nearly forever: https://www.harborfreight.com/85-gram-super-lube-grease-cartridge-93744.html