A vehicle climate control system operates an evaporator at a minimum temperature adjusted by a temperature offset. The control system determines a desired temperature and a blend potentiometer position that is indicative of the desired temperature. The control system determines a target temperature for the evaporator according to the blend potentiometer position, and calculates the temperature offset according to the target temperature and the blend potentiometer position. A blend door position is controlled according to the blend potentiometer position, the target temperature, the temperature offset, and heater core air temperature in order to optimize the operation of the evaporator.