GM LS/Gen III Dual Activ Dual Fan Relay

The GM LS/Gen III Dual Activ Dual Fan Relay by Painless Wiring is a dedicated thermal management controller designed for LS and Gen III engine swaps where OEM fan control won't suffice. Built by mechanics and hot rodders who understand that aftermarket cooling systems demand precision control, this fan relay eliminates guesswork and protects your investment by automatically engaging dual electric fans at the optimal temperature threshold. Whether you're running a carbureted LS in a classic chassis or a Gen III power plant in a custom build, this controller ensures your cooling system responds exactly when needed—no more, no less.

This dual-fan relay activates both fans simultaneously at 185 degrees Fahrenheit and disengages at 175 degrees, maintaining a tight thermal window that prevents overcooling and excessive parasitic drag on your engine. The kit includes a 3/8 NPT temperature sensor that threads directly into your intake manifold, cylinder head, or custom water neck, plus a 1/2 NPT adapter for installation flexibility across different engine configurations. Complete with relay harness and all necessary connectors, the system is ready for immediate integration—no fabrication required. The compact 7.5 x 2.25 x 12.5-inch module mounts easily in engine bays with limited space, while heavy-gauge wiring and sealed relays withstand the vibration and heat cycling of performance driving.

Street rodders, restomod builders, and LS swap enthusiasts benefit most from this controller when upgrading to dual 12-volt electric fans on non-computer-controlled engines or when factory ECU fan logic doesn't match custom radiator and fan combinations. Installation works with any dual-fan setup—pusher, puller, or split-configuration—as long as each fan operates on a single 12-volt circuit. Ideal for carbureted engines, naturally aspirated LS builds, and street vehicles where reliability trumps complexity, the Painless Wiring relay delivers set-it-and-forget-it performance that keeps coolant temps stable across idle, cruise, and hard acceleration without driver intervention.