Niterider Lumina 950 took in water now on all the time
 

This is the one with an LCD display showing run time. I rode in the rain the other day and I could see the moisture under the plastic cover for the LCD display. I hoped it would dry out. Well this morning I noticed it is “on”. I cycled through low, medium & high then off and this yellowish light turns itself back on!

I notice the Niterider has 3 screws so I am assuming I can disassemble it. I may do this just to investigate how much moisture got inside.

Can anyone speak to why my Niterider is now lit up continuously with this less than white light? Thanks.

NiteRider claims their lights are water resistant but should not be submerged. If your light dies because you used it in rain and is still under warranty, I would contact them at their website, According to their website these lights have a "limited" lifetime warranty.
"NiteRider’s Limited Lifetime Warranty does not cover normal wear and tear, abuse or normal degradation of the battery that occurs over time." It doesn't see like your light was very water resistant unless you rode it in a really bad downpour.

Set it near a fan for a few days to dry out. Open the USB port cover. If you don't mind taking a chance, you could unscew those fasteners and open the case to help dry it out.

I have a recirculating air HEPA filter -- about 18" wide, 24" tall, 8" deep -- that I use to control household dust but also to quickly and safely dry out my sweaty running and cycling shoes, and various devices after a rainy ride. Works great. It draws in air from a side-facing vent, and blows it out through a top-facing vent. So it's easy to set items on top of the air filter for drying.

If I had only a box fan, I'd set it sideways on top of something like a plastic milk crate, something to ensure plenty of air circulation all around. Set the devices on top of the upward-facing box fan. If the fan's protective grate is too large, tape some mesh or a filter on top to keep items from falling through into the fan blades.

Don't use heat. And don't bother with rice or desiccants -- those take too long and a waterlogged device will be permanently damaged by corrosion, etc., by the time desiccants work.

If you don't have a 21" CRT you can leave the light on top of (that was great for gloves too!), you might try leaving it on the floor in front of a refrigerator. (Probably not the one at work!) The fan cooling the coils keeps a gentle air current when the 'fridge is running. As canklecat notes, leave the USB cover open.

step 1 would be to try to get Niterider to replace it under warranty.
step 2 would be to open it up and see what it looks like, and take pictures so we can see too. :)

Any sort of corrosion or crud could be conductive enough to cause the circuits to malfunction. It might be enough to let it dry out, or maybe dip a Q-tip in rubbing alcohol and clean off anything that shouldn't be there.
The components themselves can absorb moisture, which generally isn't good for them. As an electronics engineer, I've never heard the manufacturers ever discuss whether they might work correctly once dried out. They tend to emphasize keeping the moisture out. :)

Steve in Peoria