Need help trouble shooting a non-working light!

Hello everyone,
I have a problem. I have a flashlight that stopped working. It is an UltraFire flashlight that takes two 3.6volt batteries. I've ordered two new light modules (tested them w/ proper voltage from a reliable source –so they are good). I've tested the tail switch with a continuity tester- it is working fine. I've checked for continuity via the switch to the other end of the tube- that's fine. The rechargeable batteries test to be 3.6 volts. This thing should work – but it's not.
Any and all comments appreciated!
Many thanks,
Bob R. Baltimore, MD

If the light modules and batts and the switch are good to go then there must be a contact problem at the module to battery area...

When I read the subject, I thought you were having difficulty using a firearm to put a non-working light out of your misery.

If this were the case, I'd have suggested something like an armor-piercing .30-06.

Good luck

Clean the threads and remove any residue or old lube that has built up. Keep the threads dry throughout your troubleshooting.

Double check your cells on a meter just to make certain. Press them gently while metering them, its possible the protection circuit in one of the cells has a cold solder joint that disconnects under pressure from the springs.

Load the confirmed good cells, and use a small wire segment and direct connect the battery "-" terminal to the body tube, just to confirm completely the body + springs are delivering power to the light engine.

If it emits consistently then the problem is somewhere in the switch-cap.
If it doesn't emit then there is a problem with the body-module contact.

Sounds like you have already metered the switch-cap by itself and it is confirmed good. However you should still make sure the switch mechanism is screwed securely into the cap. Its possible the spring force is causing an open circuit contact that ONLY exists when cells are loaded and the springs are exerting force.

You should also be aware that on the Kai & DX-like modules, the brass pill light engine should NOT be tightened all the way down into the reflector. Its counter-intuitive, but thats how they are. On my 6P I have to LOOSEN the light pill from the reflector by a turn or two to ensure proper body contact.

I fiddled with this for 20-30 minutes, at first I thought my 6P was defective, but it turned out to be just a quirk with the DX modules.

Yeah I thought you were a bad shot going by the title! LOL.
Good luck getting it to work.

Try another batteries, it should be 4.2 volts, and try a paper clip for a tail cap.