Fan Control Module
COMPONENT PARTSFan speed control system components are:
1. Auto amp.
2. Fan control amplifier
3. PBR
4. In-vehicle sensor
5. Ambient sensor
6. Sunload sensor
7. Thermal transmitter
8. A/C mode switch
SYSTEM OPERATION
AUTOMATIC MODE
In the automatic mode, the blower motor speed is calculated by the auto amp. based on inputs from the PBR, in-vehicle sensor, sunload sensor, and ambient sensor. The blower motor applied voltage ranges from approximately 5.0 Volts (lowest speed) to 12 Volts (highest speed).
To control blower speed (in the range of 5V to 12V), the auto amp. supplies a signal to the fan control amplifier. Based on this signal, the fan control amplifier controls the current flow from the blower motor to ground.
STARTING FAN SPEED CONTROL
Start up from "COLD SOAK" condition (Automatic mode)
In a cold start up condition where the engine coolant temperature is below 50° C (122° F) (except VENT and DEF modes), the blower will not operate for a short period of time (up to 126 seconds). The exact start delay time varies depending on the ambient and engine coolant temperature.
In the most extreme case (very low ambient) the blower starting delay will be 126 seconds. After this delay, the blower will operate at low speed until the engine coolant temperature rises above 55° C (131° F). Then the blower speed will increase to the objective speed.
FAN SPEED CONTROL SPECIFICATION
FAN CONTROL AMPLIFIER
The fan control amplifier is located on the cooling unit. It amplifies a 12-step base current flowing from the auto amp. to change the blower speed within the range of 5V to 12V.