What are the functions of a contactor? The function of a contactor or motor starter is simple, when the AC supply goes to the contactor coil, the coil make a strong magnetic field and field pulls the iron core to the coil and make a electrical contacts.What is inside contactor? A contactor is a small device that controls the flow of electricity to one of your air conditioner’s components. You can think of a contactor like a drawbridge that extends over a river. When the drawbridge is down, cars can drive freely over the bridge to get to the other side.What is an electrical contactor for? A contactor is an electrically-controlled switch used for switching an electrical power circuit. A contactor is typically controlled by a circuit, which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 230-volt motor switch.