HVAC Controls
Controls for the heating, ventilation, and air-conditioning system (HVAC) consist of a fan speed switch, an air vent selection switch, and a temperature control switch. On vehicles with air conditioning, the panel also contains a telltale LED and an air recirculation button as shown in Fig..
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Fan Speed
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Vent Selection
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Temperature Control
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Air Recirculation
Fig. 1, HVAC Climate Control Panel, Standard
Fan Speed Switch
The fan speed switch controls the speed of the fan that forces fresh or recirculated air through the air outlets.
In the default mode fresh, or outside, air circulates through the heating and air conditioning system. If equipped with air conditioning, recirculation mode is available. This limits the amount of outside air entering the cab.
The fan has eight speeds.
Air Vent Selection Switch
The air selection switch allows you to control the flow of air through the face, floor, and defrost vents.
Before using any of the defrost modes, clear the screen at the base of the windshield if snow or ice is present.
With the intermediate modes between each telltale, there are nine modes to choose from on a system without air conditioning, as shown in Fig. and eleven modes to choose from in a system with air conditioning as shown in Fig..
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Face Mode
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¾ Face, ¼ Floor Mode
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½ Face, ½ Floor Mode
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¼ Face, ¾ Floor Mode
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Floor Mode
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¾ Floor, ¼ Defrost Mode
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½ Floor, ½ Defrost Mode
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¼ Floor, ¾ Defrost Mode
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Defrost Mode
Fig. 2, Air Selection Switch Without Air Conditioning
Fig. 3, Air Selection Switch With Air Conditioning
Temperature Control Switch
Turn the switch to the left (counterclockwise) for cool air, or to the right (clockwise) for hot. There are 21 positions on the temperature control switch.
Recirculation Mode
Press the recirculation button to prevent dusty or smoky air from entering the cab or to decrease the time required to cool or heat the cab interior during extreme outside temperature conditions. When recirculation mode is active the LED next to the recirculation button shown in Fig. illuminates.
To prevent the buildup of odors or oxygen depletion inside the cab, after 20 minutes the system switches from full recirculation mode to partial recirculation mode for five minutes. The system cycles from full to partial recirculation as long as the mode is enabled.
Recirculation mode is not available when the air vent selection is set to partial or full defrost mode.
Air Conditioning
The four air conditioning modes are marked in blue on the air vent selection switch.
Important: Operate the air conditioner at least five minutes each month, even during cool weather. This helps prevent drying and cracking of the refrigerant compressor seals and reduces the chance of refrigerant leaks in the system.
Note: The heating and air conditioning system has a brushless blower motor with a protection or shutdown mode to prevent damage due to overheating and overcurrent conditions. If the brushless blower motor goes into a protection mode, the motor operates at a slower speed. If the overheating or overcurrent condition continues, the motor shuts down and stops completely. The motor resumes normal operation after the motor has cooled or the overcurrent condition has been resolved. It is necessary to cycle the fan switch off, and then on, to reset the motor. If the problem appears repeatedly, take the vehicle to a Freightliner dealer or authorized service outlet for repairs.