Universal 24V relays for truck, heavy-duty vehicle and professional machinery

Trucks and heavy goods vehicles operate with a 24-volt electrical circuit, made up of two 12V batteries in series. A 12V relay cannot work properly on this circuit: its coil is not sized for a 24V voltage and it may burn out. The 24V relay is specifically designed for this voltage, with a suitable coil and contacts. Using the right relay ensures reliable operation and an optimal service life for your LED installation on a professional vehicle.

A 24V 40-amp relay supports a maximum power of 960W (40A x 24V), which is more than enough for almost all LED light bars on the market, including the most powerful ones. A 300W LED light bar at 24V only draws 12.5 amps, which is less than one third of the relay’s capacity. This large margin guarantees operation without overheating, even during prolonged use. For multiple installations, a single 40A relay can power several light bars simultaneously.

Yes, the wiring diagram is strictly identical. Terminal 30 connects to the positive of the 24V battery via a fuse, terminal 87 supplies the LED bar, terminal 85 receives the switch signal and terminal 86 goes to ground. The only difference concerns the rating of the components: the relay, the fuse and the cables must be sized for 24V. In practice, since the current draw in amps is lower in 24V than in 12V, the wiring can be of a smaller cross-section.

No, a 24V relay will not work properly on 12V. The control coil is sized to activate with a voltage of 24 volts: powered at 12V, it will not generate a magnetic field strong enough to close the contacts. The relay will remain open or operate intermittently. Conversely, a 12V relay powered at 24V will see its coil overheat and burn out. It is imperative to choose a relay that matches the vehicle voltage: 12V for car/4x4, 24V for truck/heavy vehicle.

The rating of the fuse depends on the power of the LED light bar. Divide the power in watts by 24 to obtain the current draw in amps, then choose a slightly higher fuse. Example: a 200W in 24V light bar draws 8.3A; a 10A or 15A fuse is suitable. For a 300W light bar (12.5A), a 15A or 20A fuse is suitable. The fuse is always placed between the battery and terminal 30 of the relay. Never undersize the fuse (nuisance trips) or oversize it (risk of not protecting the circuit).

Yes, the 24V relays offered by AGM Vision are universal components compatible with all vehicles operating on 24 volts: trucks, heavy-duty vehicles, buses, coaches, construction equipment, military and agricultural vehicles. The mounting format is standard, with 6.3 mm terminals and a housing that clips onto a bracket. The operating voltage range tolerates normal variations in the onboard electrical system (generally 22 to 28V). No adapter is required for installation.