I bought an L2P a few months ago as a back-up to my Klarus XT-11. It was having issues with flickering, which I thought was maybe battery related, but that proved to not be the case. I then bought another tail cap, and again, same problem. The flickering is severe, it will flicker at different rates, completely shut off, and maybe come back on after a few seconds. Any ideas, or did I just get a lemon? It’s too late to send back now. BTW, I bought it directly from Solarforce.
I forgot to mention, I cleaned the terminals with isopropyl alcohol after the problem started, to no avail.
It might be the drop in module.
Yes make sure the drop in pill is screwed down tight into the reflector. Also on the L2P there is a gold insulating coating. I make sure to scrape that stuff off where the drop in ground spring rests. And with tail switch assemblies it’s good to take a pair of needlenose pliers and tighten the retaining ring on the switch.
This usually fixes flickering problems. If it doesn’t I’d be looking at a defective drop in. Many times they do a poor soldering job soldering the negative to the brass pill. I usually resolder those myself.
OK, tried your suggestions Mr Krabs, and now I don’t even get a flicker, with two different drop-ins & 2 different batteries. Gotta say I’m mighty disappointed with my one & only Solarforce.
That’s there to enhance the ground connection, not reduce it!
Make sure the reflector on your pill isn’t grounding out on the emitter connections. And yes, make sure the brass driver part is screwed in snugly for proper ground.
Going to be one of those 2 things, most likely.
I have 7 Solarforce lights, never had to scrape anything off any of them to get them to work properly, especially not the 4 L2P’s I have with that gold coating!
The host is just a tube of metal. So long as the negative end of the tube is clean and makes contact with the drop in, then it’s can’t be the host itself and must be one of the other components.
I had flickering on my L2M after about 6 months of use, it turned out to be the switch, it had become lose in the tail cap. Might be worth making sure it’s all tight and secure.
What drop ins are you using? Do you have any other hosts to try them in to see if they work ok in those?
Similar with batteries, what ones are you using, and what kind of top do they have? And do they work in any other lights that have springs at both ends of the contacts.
Hope you get it sorted.
Those Solar Force’s are HORRIBLE. Send it to me, I’ll dispose of it for you. 
Sounds, to me, like its an issue with the drop-in. I have a hard time believing that both switches came loose or with some sort of problem. I bought my SF hosts a couple of years ago and I use the 3 mode Ultrafire XML drop-in sold by Manafont that was highly recommended here. Not sure if there is an upgraded version of that drop-in, but I would order one to use in your SF. That particular drop-in was recommended over even SF’s own drop-in’s at the time. Not sure if that would still be the case since SF sells upgraded drop-ins with the new XML’s (again, not sure if Ultrafire sells an upgraded version of the one I use), BUT since you’re having issues with a SF drop-in, I can’t exactly expect you to try a new one. Perhaps see if SF will honor the warranty by sending a new drop-in. It may be out of warranty, BUT you alerted them that you had a problem while it was still under warranty, I would use that angle to try to get them to send a new drop-in under the warranty.
also look at the ends of springs — often they’re cut off with something that leaves a sharp point, and that sharp point becomes the only point of contact. I find bending the last bit of the spring slightly away from the battery, so they make contact over say a quarter inch of the side of the spring, instead of at a tiny point, often helps.
So does adding a trace of conductive lubricating gel.
Agree on tightening up both the pill and the switch, too.
Remove the tail cap and test with the paper clip trick. If it works, the problem is in the tail cap.
Disassemble the tail cap, clean, reassemble, and test.
Do not use the outer springs, they are horrible for both the ground connection and for heat transfer. Make a simple spacer ring and never mess with that crap again.
I wish somebody sold these…Copper tape is so expensive and I am too lazy to make the rings myself
I buy my copper tape from a seller on ebay that sells it as “Slug tape” apparently you put it round plant stems to stop slugs eating the leaves.
Anyway it’s adhesive backed 20mm wide and sells for £2 for 4 metres, that wraps a lot of drop-ins.
3/4" copper pipe sections about .300-.325" long, slit lenthwise and expanded a bit to be a tight fit in the head. Works on 501b-type lights too, though some have to have either the front face of the battery tube shortened a bit, or the step in the bottom of the head cut a little deeper, to let the spacer seat correctly. On those you loosen the battery tube a few turns, screw the bezel down completely, then screw in the battery tube to push the spacer + dropin forward to clamp it all down tight.
Tape is an awful awkward solution... each dropin has to be wrapped, the copper spacer stays in the light and works with any dropin. Most folks have more dropins than hosts...
Wouldn’t the spacer have to be the exact right length to both prevent rattle and allow the head to fully tighten?
I prefer to use the spring and have the reflector tightly wrapped in tinfoil for a snug fit and good heat transfer.
You’re right there, the tape is very sticky and prefers beard hairs to drop-ins. One of the bad things is the drop-in loses it’s label and I find it difficult to write with a Sharpie on a curved surface.
I’ll have to get down to the plumbers and get a few off-cuts of copper pipe.
Doesn’t adhesive interfere with thermal and electrical conductivity?
I like soda can strips lightly sanded on either side. It’s cheap and easy to cut to size.
It depends. On the L2P with a one-piece head/battery tube there has to be a small gap at the bezel when fully tightened to clamp the dropin against the spacer, an aesthetic thing I don't even notice and if I did I'd gladly accept it as the cost of having vastly better heat management. Some people are too picky to deal with things like a .030" gap around the base of the bezel and don't mind sacrificing better performance for the sake of being pretty.
Aren't most brass pills tapered after they exit the reflector? If this is the case surely the contact area would be minimal. I use copper tape or foil around the reflector but I didn't think the spring contributed much thermally.
Perahps I'm a little thick but I'm not quite understanding how the copper ring would provide much benefit. What am I missing here?