Abstract: A control for changing direction of air flow through a cooling core in response to an external signal and a purge signal includes a logic circuit and a relay assembly. The logic circuit generates a fan control signal based on the external signal, which causes the fan to turn on and operate in a cooling mode and generate an air flow through the cooling core in a first direction, or operate in a neutral mode with reduced or no air flow through the cooling core. The logic circuit also includes at least one timer that internally generates the purge signal, which is then transmitted by the logic circuit to the relay assembly. The purge signal overrides the fan control signal and causes the fan to operate in a purge mode, which causes air flow through the cooling core in a second direction opposite to the first direction.