C 3500 Truck 2WD V8-6.0L VIN U (2001)
some air will be diverted to the defrost setting to keep window fogging at a minimum.
If the ambient air temperature is less than 2°C (35°F) and the coolant temperature is less than 10°C (50°F), then a 75 second purge will occur. The
purge is performed in order to reduce window fogging until the coolant warms up. The purge will begin as soon as the coolant temperature reaches 4°C
(40°F). The mode door will move to the defrost position and the blower motor will be near half speed.
In warm temperatures, the automatic HVAC system will provide A/C in the most efficient manner. The HVAC system can quickly cool down the vehicle
when the temperature is set to minimum, blower motor is set to maximum, and recirculation and vent modes are selected. Once the desired temperature is
reached, the blower motor will slow down, discharge temperatures will be raised, and the mode actuator will be switched to bi-level for better passenger
comfort. The recirculation actuator can be partially opened to assist in temperature control. Regardless of mode selection, some air will be diverted to the
floor setting to keep occupant comfort at a maximum.
Air Distribution-Manual Auxiliary HVAC Control
If the vehicle has a sunroof (CF5), then the auxiliary mode actuator can only be controlled by the front auxiliary HVAC control assembly. The primary
HVAC control module located in the dash cannot control the auxiliary HVAC system. The vehicle operator determines the mode setting by placing a
mode switch in a desired mode position. Only upper and lower vent positions are available at the rear of the vehicle. When a mode setting is selected, a
signal is sent from the front auxiliary control assembly to the mode actuator through the mode door control circuit. The auxiliary mode actuator moves
the auxiliary mode door to the desired position. Power and ground is supplied to the mode actuator by the ignition and ground circuits.
"For a description of the RPO Code(s) shown in this article or any of the images therein, refer to the RPO Code List found at Vehicle/Application ID".
See: Application and ID/RPO Codes
Air Distribution-Automatic Auxiliary HVAC Control
Depending upon the auxiliary HVAC system content, the auxiliary mode actuator can be controlled by either of the auxiliary HVAC controls. The
primary HVAC control module located in the dash does not control the auxiliary HVAC system. If the vehicle does not have a sunroof (CF5), then the
front auxiliary controls must be set to the rear position for the rear auxiliary controls to operate. The vehicle operator determines the mode setting by
placing a mode switch in a desired speed position. Only upper and lower vent positions are available in the rear of the vehicle.
When a mode position is selected on either of the auxiliary HVAC controls, a signal is sent from the auxiliary HVAC controls to the auxiliary mode
actuator through the mode door control circuit. The auxiliary mode actuator moves the auxiliary mode door to the desired position. When the auxiliary
mode door moves to a desired position, a variable resistor within the actuator is used to create the mode door position signal. The HVAC module uses
the mode door position signal to determine the actual auxiliary mode door position. Power and ground are provided to the HVAC control module by the
fuse block through the ignition 3 voltage circuit and the ground circuits through the right instrument panel junction block. A 5 volt reference signal is
sent to the actuator through the 5 volt reference circuit, through the right instrument panel junction block, to the auxiliary mode actuator.
"For a description of the RPO Code(s) shown in this article or any of the images therein, refer to the RPO Code List found at Vehicle/Application ID".
See: Application and ID/RPO Codes
