Fan Control
PCM monitors certain parameters such as: engine coolant temperature, vehicle speed, A/C on/off status and A/C pressure to determine engine cooling fan needs. PCM controls fan operation through Fan Control (FC) on single speed fan applications, or Low Fan Control (LFC), Medium Fan Control (MFC) and/or High Fan Control (HFC) outputs on 3 speed fan applications. Although PCM output circuits for 3-speed fans are called low, medium and high fan control, cooling fan speed is controlled by a combination of these outputs. See Fig 1.