I have this with the 5 mode XM-L T6 led in it, and it is VERY BRIGHT!!! (the equivalent of a 1M candlepower spotlight or a 40W desk lamp) But after a few days playing with it, it started to jump between modes, dim out, flicker etc. occasionally, it would cut out completely Well, I read somewhere a dieing battery causes it. this is not the case. However it does appear the amount of charge in the battery has an impact.
so, me being, ME, I decided to tear apart the torch and diagnose the problem. I looked at the drop-in module... that wasn't the problem. I turned my suspicion to the switch. It seems this was the problem, so I looked around for a replacement, no luck.
my next challenge was to find out how to take apart the tail cap to get to the switch itself.
Step 1: Closer Look Inside
well, I found out how to take the tail cap apart to the point I can see the inner workings. I drew a simple diagram of what I found, and lied them out in order ( the cylindrical spacer goes inside the other washer / toroid shaped spacer)
Step 2: The FIX
I found out is the last piece was not making contact the switch. This turned it to be a very simple fix. just tighten the last part.
Without the special tool that fits in two holes I just used some brute man-power to tighten it and I never had a problem since... if you want to tighter, you can try pointed scissors or anything that fits into the hole.
please comment, and rate!
Step 3: Improve Preformance of Your Light
Stop by radio shack and pick up thermal paste and smear some on the inside of where the reflector touches the inner casing of the light next to the glass (careful not to get any on though) put the pill (reflector bulb piece) back in there and then shove as many pieces of scrap aluminum foil in around to better help with heat dissipation.
If you are using a cheap Ultrafire, Spiderfire, Trustfire, or some other cheap 18650 battery, replace it with a higher quality battery. It will set you back more than $15, but something like an AW brand 18650 would be worth it because these battery's are of higher quality, last longer, are safer, and crank out more power, (3A or more). Personally, I use Tenergy 2600 mAH. Your light will be brighter and last a bit longer.
To improve the throw, (the tightness of the beam), get another drop-in or pill with a smooth (SMO) reflector and with a XML-U2, or (a brighter led bin, a step up from the T6)