I'm guessing quality issues...
I bought a K1000 and K1200 for a trip and took them apart to make sure they would survive. Here's what I found.
The dealer had already changed out the tail cap o-rings because of problems with the o-rings being too soft, too small and leaking. He also changed out the batteries because the stock cells were proving to be unreliable.
So I took off the head and found:
1) There were two o-rings installed, even though there was only one o-ring groove. The second o-ring was in the thread relief area, which was not big enough to fit it, and it was severely cut from having the head torque on anyways. Additionally, these orings were also too small (overstretched) and extremely soft (like 30 durometer) One of the light heads had a sharp burr on the corner that passes over the o-rings before seating and the second light, someone had removed the burr and the anodizing with it, so it is sure to corrode now.
2) The spring for the detent ball under the on/off ring was highly magnetic and was corroded on one of the lights, straight out of the box. It's not a corrosion resistant material and won't last long in saltwater.
3) The magnet on the inside of the ring was simply a nickel plated neodymium magnet glued in a groove. My experience with nickel plated neodymium magnets in sea water is that the plating eventually fails and the magnet turns into a ball of rust shortly thereafter.
4) The LED was not secured to the heat sink and the thermal path between the heatsink and the housing had no thermal grease. There was a small spot of thermal grease under the LED PCB, but since it was not making solid contact with the heat sink, it was not doing much good. The LED itself was a Cree XM-L which could put out 1000 lumens if properly heat sinked, but the lack of cooling in this light will make it fall short and die sooner. There's no way the two cell light will hit 1200 lumen and was actually a little dimmer out of the box, indicating the actual LED emitters are not binned very close.
5) One of the chargers did not work out of the box and after opening the charger, I found one of the wires going to the plug prongs from the inside was not actually soldered to the prong, but just melted into the plastic next to the prong.
So I killed one LED chip trying to adjust the hall switch with the light on and shorted it out and took the second light on the trip after putting it back together. It flooded within 2 minutes of hitting the water and I quickly took it apart and managed to save most of it. I later found that a small amount of seawater got between the LED chip and PCB after the LED popped off the board revealing the cold solder joints.
I repaired both lights by replacing the LED PCBs with Cree XM-L2 units that were thicker and actually allowed the reflector to compress them onto the heatsink for better thermal contact. Probably what the original design was supposed to do, but the stock LED PCBs were too thin. To get around the corroding spring issue, I took a piece of that soft o-ring and stuffed it under the detent ball to act like an elastomer spring and it works pretty good.
These lights now reside in the shop and truck as dry use only flashlights. I was really hoping these lights would workout, as I hate the backup lights that you have to twist the head on and off, since o-rings were not meant to do that repeatedly. I guess I'll just have to design my own light now, since my hypercritical personality can't seem to find a dive light it likes. I was really hoping to avoid that...
