Hella Marine Mini ISO Relay, 12V, 5-Pin, SPDT, 20/40A, Diode Coil Suppression, IP54

Overview

The Hella Marine 007794041 is a 12V mini ISO relay with a 5-pin SPDT (Form C) contact set, rated for 40A continuous on the normally-open contact and 20A on the normally-closed contact (at 85°C). It carries an IP54 rating and uses diode coil suppression to reduce electrical noise back into the control circuit.

On a boat, this relay is a clean way to switch higher-current loads using a lower-current helm switch, keypad output, or automation trigger, without running heavy cable up to the console. It is sized for typical relay blocks and sockets and is well suited to protected electrical spaces where vibration and occasional splash are part of normal life onboard.

Key features

• 12V nominal coil with pull-in at = 8.0V and drop-out at = 1.0V
• SPDT / Form C changeover contacts (terminals 30, 87, 87A) with coil terminals 85 and 86
• Rated continuous load at 85°C: 40A (N/O) and 20A (N/C)
• Inrush capability noted for demanding starts: up to 150A (lamp) and 166A (motor)
• Suppression diode across the coil to tame switching spikes on the control side
• IP54 rating with dust cover for use in protected compartments
• ISO 8092 6.3 x 0.8 mm blade terminals with tin-plated contacts and AgSnO2 contact material

Compatibility and fit

This is a standard mini ISO, 5-terminal relay with 6.3 x 0.8 mm blades, making it compatible with many common relay sockets, relay blocks, and harness pigtails used in marine and vehicle electrical panels. The terminals are identified by the usual numbering on the relay body or socket, which helps keep troubleshooting straightforward later.

It is a 12V coil relay with a specified maximum coil voltage of 18V, so it is not a direct substitute for 24V coil relays. If your boat is 24V, confirm you have a 12V control feed available before ordering.

Installation and setup

Mount the relay where it stays out of direct spray and away from bilge water, using a supported socket or harness so the terminals are not carrying strain. Keep wiring runs to the load as short as practical and secure the harness so vibration does not work the connections loose.

Because the coil is diode-suppressed, the coil terminals are polarity-sensitive. Follow the + and - markings on the relay or socket when wiring the control side to avoid reverse connection.

Electrical and system integration

Use the relay so the high-current path stays close to your battery distribution or breaker panel, while the helm switch or control output only energizes the coil. Size wire gauge and overcurrent protection for the actual load and duty cycle, and keep continuous current within the stated contact ratings, especially in warmer compartments.

Large start-up surges are normal with motors and some lighting loads. The relay is specified for high inrush, but clean crimps, tight terminals, and correct fusing are still what make the system behave on the water.

Use cases on board

Common uses include switching deck and cockpit lights, horns, ventilation fans, solenoids, and pump circuits where you want the control wiring to stay light while the load wiring stays short. It also fits well when an electronics output is only meant to trigger a relay coil, not carry load current directly.

This relay makes the most sense for owners who want a tidy, serviceable wiring layout and an easy-to-find standard footprint when replacements are needed later.

Maintenance and troubleshooting

If a circuit cuts out under load, check the socket for heat discoloration, loose terminals, and corrosion before blaming the relay itself. A relay that clicks but does not pass power often points to a poor crimp, a loose spade in the socket, or a load that is pushing past the contact rating.

If the relay does not energize after a wiring change, confirm coil polarity at the socket since diode suppression requires correct + and - orientation.

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