The outdoor air conditioner is connected to the indoor evaporator coil by a pair of copper lines. The bigger of the two lines are insulated and usually transports a cool gas and is known as the suction line. The other line, often referred to as the liquid line, transmits a warm fluid. When the system is functioning, the suction line is supposed to be cool to touch and perspiring where insulation is absent. The uninsulated liquid line must be warm once the system has been functioning for 10-15 mins. The liquid line sensor’s function is to adjust this temperature at working levels.