The PCB, also known as an electronic control board, monitors air temperature in the room and turns the compressor on or off accordingly. The thermostat is connected to the control board and will extend to the front of the evaporator coil. If your air conditioner is not blowing cold air and after inspecting the air filter and fan motor, yo...Read moreu found them in working order, there may be a problem with the PCB. If the control board is defective, it may not send power to the compressor, and no cooling will take place. Inspect the thermostat first for any signs of damage or corrosion before condemning your PCB.