Sierra RK40620B Blue LED Rocker Switch | 12V 20A SPST

The Sierra RK40620B is one of those parts you don't think about until you need it, and then you're glad it's built right. It's a 12 volt, 20 amp single pole single throw rocker switch with a blue illuminated halo, wrapped in a black rectangular housing that drops into a standard rocker panel. On-off, plain and simple. Flip it up, the circuit's live and the blue ring glows so you can find it in the dark. Flip it down, everything's off.

We reach for switches like this all the time when we're rigging up accessory circuits. Deck lights, a livewell pump, a set of spreader lights, an accessory 12 volt outlet, a stereo amp remote. Anything you want a clean, positive on-off for. The blue halo isn't just for looks either. On a night run, being able to glance down and see which circuits are hot without hunting for a label is worth a lot.

This is a single pole single throw switch, which is the marine way of saying it does one job. It opens or closes one circuit. There's no on-off-on, no momentary spring-back, no second position. So if you're wiring something that needs to reverse or needs a center-off, this isn't the switch for that. For a straight accessory you turn on and leave on, it's exactly right. Sierra also makes an SPDT version in the same body if your project needs the extra throw.

Wiring is straightforward. You've got three blade terminals on the back. One feeds power in from your fuse block, one sends power out to the accessory, and the third grounds the LED so the halo lights up. Run it off a properly fused circuit, size your wire to the load, and you're set. For most accessory runs on a small boat, 14 gauge tinned wire pairs nicely with the 20 amp rating. We always tell folks to hit the spade terminals with a little dielectric grease before you snap them on. Terminals live a hard life in a damp console or locker, and that dab of grease keeps corrosion off the copper.

About that 20 amp rating. It's an honest number for a resistive load like lights. But motors and pumps pull a big inrush spike when they start, so if you're switching something inductive like a bilge pump or a washdown pump, give yourself margin and keep the continuous draw well under the rating. Better to run a switch cool than to cook the contacts over a couple of seasons.

One quirk worth knowing with illuminated rocker switches in general. Some owners notice the LED still glows very faintly when the switch is off. That's a tiny bit of leakage current through the lamp circuit, it's harmless, and it doesn't mean the switch is bad. On a big battery bank you'll never notice it. On a small bank where you're counting every amp-hour overnight, just know the halo sips a few milliamps whenever the circuit's energized.

It's a snap-in rocker, so it seats into a rectangular cutout and holds with the housing tabs. On a hard-running planing hull, vibration can eventually work snap-in switches loose, so a lot of us put a small dab of adhesive at the corners once we know the placement is right. One more honest note. The data we have doesn't list a waterproof rating on this one, so treat it as a behind-the-dash or protected-panel switch. If it's going somewhere it'll catch spray, add a rubber rocker boot over the face and you're covered.

For the money, it's a solid, no-drama switch from a brand that's been supplying marine and OEM electrical parts for decades. It won't be the flashiest thing on your dash. It'll just work, night after night, which is exactly what you want out of a switch.