Blue Sea Systems HD-Series Selector 3-Position Battery Switch with AFD

The Blue Sea Systems HD-Series Selector Battery Switch lets you isolate battery banks to separate loads, or combine them into one for charging and emergency starts, all from a single 3-position knob. A make-before-break contact design means switching between banks never interrupts power to whatever's running.

Key features

• 3 positions, 500A continuous, 700A intermittent (5 min)
• 2750A cranking (10 sec), 32V DC maximum
• 1/2" (M12) tin-plated copper studs, torque 220 in-lb (24.86 Nm)
• Ignition protected, IP66 rated, one-piece stud design never loosens

This switch includes Alternator Field Disconnect (AFD), which protects the alternator's diodes from damage if the switch is inadvertently turned to Off while the engine is running — a genuine safeguard against a costly repair.

Torque the terminal studs to 220 in-lb (24.86 Nm). This is an Off-1-2 switch without a combine ("both") position — for that, the 4-position HD-Series selector (PN 3002 or 3003) is the correct choice instead. It accepts two 4/0 AWG battery cables per terminal and shares the HD-Series' 500A continuous rating, the highest in Blue Sea's manual battery switch lineup. An optional ICON label kit is available for customized position labeling on most models in this family, and mounting works equally well on a flat surface or a rear panel depending on the installation.

Check the terminal connections periodically for tightness and corrosion, especially on a switch handling this much current — a loose stud is one of the more common sources of resistive heating in a battery-switching circuit that sees frequent use.