Almost 2 years ago I bought a TH20 for backpacking. It has not seen that much use as I haven’t been backpacking much until recently, and I purchased a 18650 headlamp that has been getting most of the use.
After last weekend’s backpack I open the TH20 to change the rechargeable. Trying to screw it back together I notice the o-ring had swollen. After some fumbling I decide to remove the o-ring, and after screwing back together I notice it does not work.
Shorting the battery to the case with a screw the light works. I removed and reinserted the spring in the lid and checked for continuity - all good.
The problem has to be at the body to lid contact area.
Any others with this problem? How did you fix it?
RMA it. Fixed once for good.
Seems like it could be misalignment or corrosion.
Clean the contact area on both surfaces, maybe something like Scotchbrite but be careful about where the bits that come off go. Maybe just a q-tip and alcohol in the cap.
Does the spring look like it comes out perpendicular to the bottom? Since the battery is not centered it could go awry if it is deformed in any way.
I cleaned the contact surfaces, the spring is straight.
edit: I just tried 2 layers of aluminum foil and that is enough for contact.
It seems that either:
- The threads stop before the cap bottoms out
- The anodized surface is making contact instead of the bare aluminum surface
When you screw the tail cap on does it reach the end with a solid stop or is it mushy at the end of travel?
Have you tried different batteries in the event that the shrink-wrap or nipple design is causing a poor connection?
Maybe try rotating the spring inside its groove 90 degrees and test. If nothing try a couple more times.
It is subjective, but I don’t think the end of travel is mushy.
I have tried 3 different Fujitsu and one Sony rechargeable, no change. It ran fine on Fujitsu before.
Rotating the spring is clever 
but it has made no difference. I tried leaving one “leg” of the spring out of place so it would make direct contact with the headlamp body and it didn’t work, which points to theory #2 above.
Did you make sure the body is facing the correct direction? One time I took the head, body, and tail apart to clean the contract, but stopped working when I put it back together. An hour of troubleshooting later and I realized I put the body back together backwards.
Hours before I left on another backpacking trip, as I tried to fall asleep, it dawned on me - what if I got the caps switched?
And sure enough, the TH20 had the H03 cap and vice versa. It also explains why the o-ring had “swollen”. Obviously the TH20 works fine with the right cap. I regret bending the seating area of the Skillhunt H03 cap, making nicks in it, but it still works. I had ordered a black Eagle Eye H1R as a replacement before I figured the switch, more black caps to mistakenly switch 
Sorry to have wasted people’s time and thanks to those that have tried to help!
Now to create another username, free of the past 
I can assure you that all of us have made similar mistakes. I’ve made some dandies! 
It’s just that most of us never admit it! 
Wow, what a funny story! To think that the Skilhunt H03 cap is compatible… curious. I have a TH20 that is languishing in a box, slated for a future emitter mod. But I also have a Skilhunt H03 RC. Despite the H03 cap not working right on the TH20, does the TH20 cap work OK with the H03 and not cause any damage?
Btw, isn’t the H03 a terrific light? Great value for the price. I actually avoided this brand for a name that I think is silly… which is a rather petty, stupid reason, but an easy one given the confusing array of so many LED flashlight brands. Have to filter it down somehow. 
Totally changed my opinion of the brand now that I’ve had the H03 RC for more than 6 months. I keep it in my car for all kinds of duty.
I was unaware of the cap change, so I used the H03 with the TH20 cap for a week, including a 6 hour night hike; I haven’t noticed any damage yet.
I agree, the Skillhunt H03 is great, I use it all the time - from clipping nails to car work and night hikes. The TH20 went to wife duty once I got the H03.
That’s good to know — TH20 cap can serve as a stand-in just in case. A forward facing while standing flashlight is a nice feature and these headlamps can be very handy for everyday use. Great, useful beam pattern. The pebble optic is something I’ve grown to like (it’s also on the Lumintop Geek). The UI is pretty decent too. I really don’t mind long press to off, while some people can’t stand that.