haveyou got a multimeter ?
check the switch is working, one test probe on the tail switch side bit, tube! and one in the spring , click and see if there is a connection
also check the brass rings are tight
btw god morgan from your friendly finnish neighbour
Head and tail is tight.
Will check the switch now!
Hmm, seems the switch is faulty. I probed between the spring on the driver and the outer tube/body. Nothing.
Prob spring and silver metal bit inside the tail cap
Contact.
Take off the cap, (charged) battery inside, then use a key or anything metallic to short from the (-) end of the cell to the edge of the tube.
“Practice” on a good/working light to know what technique works and what doesn’t. Too easy to lean on an anodised portion and “nothing happens”.
Nothing happens.
hm sucks… maybe write in this thread where Simon (convoy owner) is active see what he suggests maybe?
where did u buy the light ,banggood ?
Yes, Banggood.
I also ordered the Astrolux EC01 and that´s working fine.
Ok, I will write in the thread you posted.
Thanks all for the support so far! 
can you solder?
Yes, no problem. I will solder it during the day and post back with the results.
Is the driver glued in or something? I will try to disassemble it to make it easier to work on.
Turned out that the only way to remove the LED is to desolder the wires. Anyway, it was quite easy to poke the iron down there.
And success!!
Thank you all for the support. Seems to be a great forum
Woo Hooo!
wow i wish i had the skills do to that kind of stuff, good u got it worked out.
I too have a 4000K M3 and am a HUGE fan of it. One of my favorites by far. Enjoy!
Yes, it´s a great lamp.
Really like the simple UI and the tint. And the output is more than enough
Welcome! Trust me, if you can solder already, you’ll fit right in 
Yeah other than with a hot-air reflow station (I think that allows for it at least), desoldering the MCPCB and removing it is the only way to reflow an LED.
Cool! Glad to see you were able to isolate the problem and fix. If you can solder, you’re gonna love hanging out in the mods section. :sunglasses: