ENGINE MANAGEMENT SYSTEM – Td6, DESCRIPTION AND OPERATION, Description. To control the cooling fan, the ECM sends a Pulse Width Modulated (PWM) signal to the cooling fan ECU. The frequency of the PWM signal, which is varied by the ECM, is used by the ECU to determine the output voltage supplied to the fan motors. The ECM operates the fan in response to inputs from the ECT sensor, the air conditioning (AC) switch and the AC pressure sensor + AIR CONDITIONING, DESCRIPTION AND OPERATION, Operation. The speed of the electric cooling fan is also influenced by vehicle road speed. The ECM adjusts the speed of the cooling fan, to compensate for the ram effect of vehicle speed, using the CAN bus road speed signal received from the ABS ECU. When the engine is switched off, the ECM maintains the cooling fans in an active condition for up to 8 minutes. If the temperature does not reach a predetermined value within 4 minutes, the ECM will terminate the active period. If the fans are active and the temperature falls below a predetermined value, the ECM will terminate further fan operation.
COOLING SYSTEM – TD 26-1-10 DESCRIPTION AND OPERATION
COOLING SYSTEM – V8 DESCRIPTION AND OPERATION 26-2-1