Fan Switch
The fan switch activates the fan, which forces outside air or recirculated air through the air outlets. The fan switch has ten fan speed settings and an OFF position. See Fig..
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Recirculation Button
Fig. 1, Fan Switch
To operate the fan, turn the fan switch clockwise to increase airflow; turn the fan switch counterclockwise to decrease airflow.
There is a two-second delay between the time the engine is started and the blower is operational. It can take an additional four seconds for the blower to reach high speed. The blower motor performs a self-test immediately after the engine is started, which causes the delay.
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. See Idle Shutdown Timer for more information.
Recirculation Mode
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. An amber indicator on the recirculation button will illuminate when the recirculation mode is activated.
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 60 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 60-minute timer.