Problem with Klarus XT series "Tactical Mode"

Hi all,

Does anyone have long-term experience with the Klarus XT2CR (or its siblings with the same tailcap)? I have an odd problem with mine and I'd like to get some advice...

I've been EDCing this light over Winter and typically have it in my jeans pocket for around 10 hours per day. I have the light permanently in "Tactical Mode" and generally it works just fine.

However I'm noticing that there might be a bug in the firmware because after carrying it for a few hours the brightness selection becomes glitchy.
The main rubber switch always seems to work, but the "paddle" switch seems to jump several brightnesses and I never know what I'll end up with. Strobe always works flawlessly.

Unscrewing the tailcap and re-tightening it again solves the problem. I'm assuming this is enough to reset the microcontroller inside the light and all is well again until the next day.

I don't think it is the switch itself causing the problem. It seems to be related to the amount of time since the end-cap was last screwed down (I normally loosen the tailcap to lock it out overnight).
The light gets tested each morning to prove it's working right, it always is! But a few hours later it's gone screwy again.

I tried contacting Klarus ages ago but they didn't help at all, they were deeply unprofessional too (it's out of warranty now anyway fwiw).

Has anyone else had weird problems like this with the XT Series?

Is it possible to get access to the microcontroller to update the firmware? I love this light and I want to try to fix it or find out exactly what's going wrong with it. I'm 80% sure it's a firmware problem.
As it stands I cannot regard this as a tactical light because I cannot rely on it to work properly in an emergency.

Any and all advice is gratefully received.

Cheers.

W.

I've had a Klarus XT2A with Energizer Lithiums in my backpack for the last 6 or 7 years solid. I keep the tailcap loose as you do for lock-out. It always seems to work fine.

I recommend since you carry it all the time, disassemble the tailcap carefully, clean it out with ahlcohol, let dry and reassemble.

I too recommend a thorough cleaning as my XT11GT also has not had any similar problems. Not with the original tail cap anyway. Interestingly though, I bought the 360 tail cap for it and tried it out for a while but ended up going back to stock as I actually did end up with some very similar results while using it. I did however trace all of the problems back to the way the secondary switch works in the 360 tail cap. Several times the light came on while in my pocket from relatively gentle bumps to the switch and it would jump several intensity levels with what I thought was only one press.

What I discovered after further testing and opening it up is that the secondary switch is simply too easily closed and because of the controller and how the UI works, it results in the light being turned on in pockets and getting rapid button presses when not trying to do so. It was very disappointing because I love the ergonomics and design of the 360 tail cap.

Since you used the CR designation I'm guessing that it is relatively new, so likely the same type of tail cap that is on my 11GT. Thinking a bit more though I realized I did have some issues a while back that may have been similar to yours. I took off the tail cap and cleaned the threads and top of the tube as well as the inside threads of the cap and it fixed the problem.

I noticed that my Klarus tends to build up a lot of gunk from the wear on the threads and I too used to lock out the tail cap frequently. I don't have a need to anymore but I wonder if the problems you are seeing are a direct result of the frequent turning of the cap and build up of gunk on the threads and the top of the secondary tube.

Also, as you likely have not disassembled yours yet, there are actually control chips in the tail cap... not just simple electrical contacts. Also, the switch internals may be rather difficult to get loose so try just thoroughly cleaning the contact surfaces first.

lightfooted said:

Also, as you likely have not disassembled yours yet...

Click to expand...

Correct, I'm going to have to make a tool out of thin sheet metal to slot into a pair of lugs on the internal barrel of the tailcap. It's not the same as the older versions.

lightfooted said:

...there are actually control chips in the tail cap... not just simple electrical contacts.

Click to expand...

I don't suppose you happen to know exactly what those chips are do you (e.g. manufacturer part numbers, perhaps a photo)?

Sorry, I don't have any pics and it's been a while since I did it. I was going to open it up but had to get ready for work. Yeaaah...specialty tools. I really wish so many manufacturers weren't so scared of the customer being able to open things up.

Fair enough

If it turns out to be an AVR microcontroller then I might have a go at making new firmware for it. I never did like the "strobe stays on if you hold the paddle down for 2 seconds" feature. I'll upload pics at some point.