A/C systems function to keep your car cabin warm in the winter and cool in the summer. The air conditioning system additionally offers a dual function of operating your defrost in the winter months. Heating systems are made up of a heater core that acts like a small radiator behind the dash, fan, and hoses that operate the warmth from the engine to the center. Unlike house cooling and heating systems, your heater and air conditioning do not completely operate off electrical elements. Heat is controlled by an opening and closing thermostat that allows hot coolant into the heater core. Then a fan blows air through the heater core moving hot air into the cabin. Air conditioning systems function similarly, by delivering coolant to the fan to blow chilly air in the cabin.