Radiator Fan Control Relay
Radiator fan control relay may be referred to as radiator fan control module. Relay is a solid state relay. Relay controls operation of radiator cooling fans. Radiator cooling fans will operate at variable speeds depending on engine coolant temperature and the A/C system pressure. PCM pulses ground (control) circuit to signal requested fan speed. Radiator fan control relay is located near driver's side frame rail and air cleaner lower mount. See Fig 1 .
Radiator fan control relay receives constant battery voltage from fuse No. 24 (40-amp) in power distribution center. The Powertrain Control Module (PCM) controls the ground circuit for radiator fan control relay by using a pulsed (time on) ground. This pulsed ground is known as Pulse Width Modulated (PWM) ground. The PWM ground causes radiator cooling fan relay to produces a proportional output voltage for operating radiator cooling fans at different speeds.
Radiator cooling fans operate at high speed when engine coolant temperature is approximately 225°F (107°C) and then reduces to low speed when engine coolant temperature decreases to approximately 214°F (101°C). Radiator cooling fans will turn off when engine coolant temperature decreases to approximately 199°F (93°C). Also, when the A/C pressure sensor closes at approximately 275-295 psi (19.3-20.7 kg/cm2 ), radiator cooling fans operate at high speed. When A/C pressure decreases approximately 40 psi (2.3 kg/cm2 ), A/C pressure sensor opens and radiator cooling fans operate at low speed.