Fenix HP10 water resistance issues

My caving club recently bought 4 HP10s and they seemed to have good water resistance as I dunked them under water in caves and washed them in buckets. However, the day after a wet cave, one of them would turn on and go straight to turbo and couldn't be turned off without removing the batteries and it wouldn't change modes or drop out of turbo after 3 minutes. I had to use a backup light to avoid burning out the LED. Later that day, the inside of the lens had fairly visible condensation, so definitely a water problem.

I decided to give the 3 remaining HP10s a thorough test, so I left them on turbo until they dropped down to high (i.e. 3 minutes) then turned them down to low (to get a large temperature drop) and then submerged them in a bucket of water (approx 30cm deep). I left them in there for about 10 minutes and alternated between turbo and low every few minutes.

All of them showed some initial condensation on the lens which quickly burns off - I'm guessing this is the residual moisture in the head unit when it was sealed. The second HP10 failed in the same way as the first (turns on to turbo and can't turn off or change mode) but not immediately, it wasn't until the next morning that it did this. The third got visible condensation in it (which is still there after a few days) but still works fine. The fourth shows no sign of water entry.

So out of 4* HP10s only 1 didn't get water in it. If anyone out there has a HP10 and is willing to do the above test I'd appreciate hearing your experiences. I'm going to contact Fenix about this issue so it would be nice to have a larger sample size to know how common this problem is.

Submerging while hot is the culprit. The inside of the body before submersion is about equalized (Pressure) with the outside air but after submersion it has a slight vacuum. Water would tend to seep in in these conditions.

Mark, you make a good point as this is a common problem divers can have when they start a dive after their light has been lying on the dive-boat in the sun. It has heated up, even when not switched on. This happens with camera-housings too.

Speleus induced exactly this problem with the experiment he did. In normal caving circumstances, a light used for caving is going to get warm or hot in use before being submerged or dunked in what is likely to be quite cold water.

It is a little concerning that 3 out of 4 of these HP10s seem to have fallen short of the standards cavers need to expect of a good headlamp.

Speleus - very good 1st post - welcome to CPF!

Yes, I was trying to achieve a vacuum in the test. In hindsight it was a little too extreme - I should have started with a 10 minute dunk on medium with no pre-heating.

I was fairly confident that they'd survive and therefore hoping to show that the in-cave failure was just a bad unit.

Gentlemen, I am looking at getting a Fenix HP10. I would probably not ever use it for caving, save for an occasional trip into family friendly caves, and more than likely NEVER submerge it in water longer than it takes to grab it if it accidently falls in. I kayak a lot and it may get wet then but never submerged for longer than a few seconds in shallow water and probably not when it is hot. My intended use would be camping, riding, kayaking, hiking... i just want a considerably bright headlamp with lots of options as far as output goes. I have a TK40 and love it so i want the counterpart in a headlamp. Is the HP10 able to be aken apart for cleaning as far as o rings and contacts go? Is this a good headlamp decision? Thank you.

jake,

you'll probably really like the HP10. But other than the battery box, it is a sealed unit (debatable by the tests in this thread) and there is no user-maintenance that would be suggested.

A little silicone grease on the o-ring for the battery box would be a good idea though

Jake,

A friend of mine never got more than 3 days of life out of a PT Apex (water intrusion - once inside a dry bag that leaked during a rafting trip).

The HP10 has survived about 2 months.

I was snorkling the other day with both my HP10 and my TK40.

I stayed near the surface, probably didnt dive more than a meter below the water, but still, this is dynamic water pressure we are talking here while snorkling, not static.

Anyway, both held up fine, so signs of water intrusion in either.

When I first receive all my torches (unless I KNOW they wont be waterproof, ie, gerber headlight) I do an initial submersion test for about 30 minutes in a sink of water (probably 10cm below the surface), so they had both already survived that.

I have never put my torches hot into cold water though...