This heavy-duty SPST relay harness system is engineered for reliable performance in 12V DC automotive and marine applications. Featuring color-coded wires for foolproof installation, this 40A relay comes with premium socket harnesses that make integration seamless across trucks, vans, boats, and motorcycles. The relay boasts impressive specifications including silver alloy contacts with ≤100MΩ resistance, ensuring consistent operation through 100,000 electrical cycles. Operating efficiently between -55°F to +158°F, it delivers rapid 15ms activation and 10ms release times. The compact design combines high sensitivity with minimal power draw of just 1.8W while handling substantial 40A loads. With 1500VAC isolation between coil and contacts, this relay provides robust circuit protection. The complete kit includes mounting hardware and is ideal for controlling fans, lights, and other vehicular electrical accessories. Built to withstand demanding automotive environments, this relay maintains reliable switching performance even under challenging conditions of humidity and pressure variations.