Ultra Fire C3 dimming

Hi, I know you can't expect the world from cheaper brands of flashlight however, my C3 (not really such a terrible flashlight) all by itself decides to dim periodically. It dims by about 70%. When you turn it off then on again this can sometimes re-energize it. Changing the batteries-testing for short circuits, multimeter, I've done the lot and it all checks out fine. Can anyone guess what reason there is for this puzzling problem?

What batteries are you using, and what version of the C3?

At the moment I'm using 2 Vapex 1.2v rechargeables. The C3 is a single mode containing a Cree P4 XR-E emitter. I can't say much for the driver board its too small for me to specify. It has the extension tube so I can use 1 or 2 AA's. Ive had the same problem even with alkaline cells.

The problem you describe is typical for the alkaline discharge curve. If I had to guess, it would be bad due to bad cells in either case.

My guess would be that the Cree & it's star isn't properly mounted to the pill & is overheating (thus dimming). That's just my guess. You could verify that be unscrewing the pill out of the head. If that's the problem then it would be an easy fix.

Sounds like the QC/build of these lights has really come down. When they first came out, I liked them quite a bit & regularly gave them out as gifts.

-AZ

(Marduke) Could you possibly go into a little more detail for me?, this sounds interesting.

Alkaline cells cannot hold a constant discharge curve well. They will quickly dim in most lights, but perk back up after a rest. You can see the declining output on the discharge curve for alkalines on the C3 (blue curve)

https://www.candlepowerforums.com/posts/2207113

Thank you for the graph.

Hi,

I had got the same problem with my UF C3... After having disassembled the pill, I discovered that a thread of the + wire to the led emitter was randomly touching the pill body and thus created a "bad" short circuit dimming the led...

I finally decided to remove the driver and did this "wonderful" mod (wonderful at least for me )

JP

Just my experience with some of these lights may contain the answer that you are looking for.

My C2 5-mode Q5 sometimes also dimms the light. I take everything appart, sand some areas, solder the circuit, check the switch, etc. I usually get it working fine for a few more weeks before it starts again. What I have found were either poor contacts due to over anodising, reflector touching the solder points, loose switch assembly, soldering between circuit and heat sink, battery voltage getting low.

My MTE Rebel was fine in the beginning, but dropped to less than 25% output after a few months of usage. The problem was identified as the circuit after swapping, testing, shorting with wires, etc. Sometimes it briefly went brighter and then dimmed again. In the end I replaced the driver and my problem was solved.

Hope you find the solution.