I own a Serfas USL-5 raider usb headlight. This failed after very heavy rain, the blue charge light lights, but the switch won't produce light? What should I do.

  • 2
    Does the manufacturer cover water ingress? I mean - is it rated as waterproof? Might be a warranty replacement.
    – Criggie
    Commented Jun 8, 2016 at 0:15
  • There are a couple reviews on Serfas's website complaining that their light failed in the rain. I'd write Serfas and ask for a replacement - it's not reasonable for a bike headlamp to not stand up to rain.
    – Johnny
    Commented Jun 8, 2016 at 1:02
  • In my experience the light stands up to normal, but not torrential cyclone flashflooding rain. It was working when I got home from shift, after 2+ hours in torrential. I'm not unhappy with the product. Commented Jun 8, 2016 at 1:15
  • 1
    You are much more understanding than me -- a light that fails in the rain (even torrential rain) is worse than useless in my opinion since it will fail in exactly the kind or weather where it is most important. Both of my primary lights are nearly 5 years old and have been through many rainy rides without a problem (one spent 2 years permanently attached to my handlebar and was parked outside even on rainy days), and I'd expect any name-brand headlight to withstand any amount of rain.
    – Johnny
    Commented Jun 8, 2016 at 17:25

2 Answers 2


Don't attempt user service. The rubber front-piece doesn't give access to the body, the case body is tightly shut, and there is no way in through the power button. All you'll do is ruin the pre-existing water resistance by damaging the seal on the rubber front-piece.

Do leave the light indoors in a dry area and allow natural movement of moisture to clear the light. In some cases this will allow the light to return to normal functioning after 2-3 days or more.

If you have removed the rubber front-piece, carefully and gently use a flat nose screwdriver or plastic probe to lift the plastic body of the light and try to use finger pressure to cram the rubber gasket back into place. It will be held by plastic alligator style jaws that come together when the body of the light reseals. Just be gentle and keep at it and you'll get most if not all of the way there eventually.

  • 1
    I've had good luck with the let it dry approach for a decent number of lights. Bit annoying, but thats why you should always have a few lights.
    – Batman
    Commented Jun 8, 2016 at 15:12

Depends on how handy you are with a multimeter, soldering iron & electronics in general. Whatever you do, do not attempt to solder to, open, modify or repair the battery in any way. That would be dangerous.

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