Hella Marine SPDT Mini Relay, 12V, 20/40A, 5-Pin, Dust Cover

Overview

The Hella Marine 933332051 is a 12V Mini ISO changeover relay (SPDT/Form C) rated for 40A continuous on the normally open circuit and 20A on the normally closed circuit at 85°C.

It is a straightforward way to switch higher-current accessories without running full load current through a small helm switch. On board, that often means deck and spreader lights, horns, washdown pumps, or other loads where keeping voltage drop down matters.

The relay uses five 6.3 mm blade terminals in the standard 30/87/87a (load) and 85/86 (coil) layout, and it includes a dust cover with an IP54 rating for basic splash and dust protection.

Key features

• 12V nominal coil with max coil voltage of 20V
• SPDT/Form C contacts with 40A continuous rating on N/O and 20A on N/C (at 85°C)
• Max inrush load rated to 150A for short startup surges
• Operate time = 10 ms and release time = 5 ms
• Ambient temperature range -40°C to +85°C
• Mini ISO footprint with 6.3 mm blade terminals for common 5-pin relay sockets
• IP54 dust cover to help keep spray and debris off the terminals in sheltered mounting spots

Installation and setup

Mount the relay in a dry, protected area such as behind the dash, inside a console, or in a covered locker. Use a properly sized fuse or breaker on the feed to terminal 30, and keep the high-current run as short as practical between the power source, relay, and load.

Terminal 87 is the normally open output, and 87a is the normally closed output. Terminals 85 and 86 are the coil connections that can be switched by a low-current control circuit.

This relay has no built-in coil suppression, so if the trigger circuit is connected to sensitive electronics, add the suppression method your system requires.

Compatibility and fit

This is a 12V relay, so it matches 12V DC boats and accessories. It uses the standard 5-terminal Mini ISO/SPDT layout with 6.3 mm blades, which keeps it compatible with many off-the-shelf relay bases and harness sockets. For longevity, avoid mounting locations that see regular washdowns or bilge water.

Use on board

It suits boats where a small switch or control output needs to command a heavier load, like spreader lights on a mast, deck floods on a hardtop, or an accessory circuit that you want switched from a protected control point. It is a practical fit when you need a changeover relay with a 40A normally open rating on a 12V system.

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