Fan Switch
The standard cab climate control panel has a fan switch with a recirculation button, temperature control switch with an air conditioning (A/C) button, and a mode control switch. See Fig.. If equipped, sleeper cabs have a bunk override button.
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Fan Switch
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Temperature Control Switch
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Mode Control Switch
Fig. 1, Cab Climate Control Panel
The fan switch activates the fan, which forces fresh air or recirculated air through the air outlets. The fan switch has eight fan speed settings and an OFF position. See Fig..
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Recirculation Button
Fig. 2, Fan Switch
To operate the fan switch, turn the fan switch clockwise to increase airflow; turn the fan switch counterclockwise to decrease airflow.
After the engine is started, there is a two-second time delay before the blower is operational. For the blower to reach high speed, it can take an additional four seconds. 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 Engine Protection—Warning and Shutdown for more information.
Recirculation
Recirculation mode limits the amount of outside air entering the cab. Press the recirculation button to prevent dusty or smoky air from entering the cab. See Fig.. Recirculation mode can also decrease the time required to cool or heat the cab interior during extreme outside temperature conditions. When the recirculation mode is turned on, the amber indicator on the recirculation button will illuminate.
The recirculation button will not work when the mode control switch is in either defog or defrost modes.
Note: To prevent the buildup of odors or oxygen depletion inside the cab, the system switches from full recirculation mode to partial recirculation mode after 20 minutes. In extremely dusty or smoky conditions, the partial recirculation mode can be overridden by pressing the recirculation button twice to obtain full recirculation mode. This resets the 20-minute timer.