TK40 tail switch not activating light after checkn' in bag on plane 4 hours


Newly Enlightened
Oct 22, 2009
So anybody else had it not work after flying with it in the decompressed portion of the plane?

sucks, where do I go to fix?


Jun 30, 2006

Silly and funny at the same time? In any case, it's not very helpful.

OP, check the tk40 threads ... there is a "common" problem with the tk40 (about the only thing really) that happens from time to time.

Check the battery carrier ... there are "round bars" internally (black color?) that when they become "loose" somehow it affects the connection of the carrier itself.

This happened to me and other tk40 owners.

Just reach inside the battery carrier and manually tighten the long black bars clockwise (or counter, I don't remember exactly) and see if that fixes your problem. If that doesn't then definitely go through the link provided for troubleshooting.

I had my tk40 collecting dust for awhile with intentions to get it sent in ... by chance I stumbled upon that thread and voila! my tk40 works beautifully again.


Flashlight Enthusiast
Mar 9, 2011
1,651 I have 2 tk40s that I bought a long time ago. One day I got an unsolicited package in the mail. Whoever I bought it from had sent me a new battery pack. I put it in and have not had any problems. You've received some good advice. The battery pack would be the first place to look. Use your VOM and check voltages at every connection. Check the total voltage while wiggling the pack. There have been reports of the pack getting loose because of loose nuts holding it together. Use a screwdriver to bridge from the body (with the tail cap off) and the battery carrier. Push it in a little. Wiggle it some more. It should be an easy fix. Frustrating isn't it?