What controls the ac fan relay?

The AC fan relay is primarily controlled by the vehicle's climate control system, which includes the thermostat and the engine control unit (ECU). When the temperature reaches a certain threshold or when the AC is activated, the ECU sends a signal to the relay to engage the fan. This allows the fan to operate, helping to cool the condenser and maintain optimal operating temperatures for the AC system. Additionally, some systems may have temperature sensors that provide feedback to the relay for more precise control.