Fan Switch

The fan knob activates the fan, which forces air through the air outlets. The fan knob has ten fan speeds and an OFF position. See Fig..

To operate the fan knob, turn the knob clockwise to increase airflow; turn the fan knob counterclockwise to decrease airflow. If the vehicle has Optimized Idle, the fan will not operate with the key in accessory mode. Optimized Idle may also turn the fan off to reduce stress on the batteries. Refer to the Optional Engine Systems chapter for more information.

Fan Knob

Temperature Control Knob

Air Conditioning Button

Fig. 1, Sleeper Climate Control Panel

When the cab air conditioner (A/C) is on, it is normal for the sleeper fan to operate at low speed even if the sleeper fan knob is in the off position. This is necessary to protect the evaporator in the sleeper heater and air conditioner system from freezing. At lower fan speed settings, a slight increase in airflow levels may appear at times, as the control acts to regulate the evaporator temperature.

When the park brake is set, any temperature or blower speed setting changes on the bunk HVAC unit control panel will be mimicked by the front HVAC unit. For example, if you set bunk blower speed to HI and the temperature to COLD, the front unit will also operate on HI/COLD.

When the park brake is not set, the front and rear HVAC settings function independently, unless the bunk override button is pressed, or "minimum AC support" is required.

Minimum AC support is when the front unit is off and the bunk unit is set such that AC is requested (needs the AC compressor to run). In this case, the front unit will go into minimum AC support mode by operating the front blower at minimum speed to prevent the front unit evaporator from freezing up. This is also true, if the rear unit is off and the front unit is set such that AC is requested, in order to prevent the bunk evaporator from freezing up.