RAM 3500 HD Truck 2WD L6-6.7L DSL Turbo (2008)
Housing Assembly HVAC: Description and Operation
DESCRIPTION
All models are equipped with a common HVAC housing assembly that combines A/C and heating capabilities into a single unit mounted within the
passenger compartment. The HVAC housing assembly consists of the following:
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HVAC housing - The HVAC housing consists of an upper housing (7) and a lower housing (10) that are attached together by screws and is
mounted to the dash panel behind the instrument panel. The HVAC housing contains the heater core (9), A/C evaporator (15), blend-air and mode-
air doors, and has mounting provisions for the air-door actuators (3, 5, 6 and 8), floor distribution duct (4), blower motor (13), blower motor
resistor, foam seals (12, 14 and 16) and the HVAC wire harness (11).
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Air inlet housing - The air inlet housing (1) is mounted to the right end of the HVAC housing and contains the recirculation-air door and has
mounting provisions for the recirculation door actuator (2).
The heating-A/C system is a blend-air type system. The blend-air doors control the amount of conditioned air that is allowed to flow through, or around,
the heater core. The dual zone heating A/C system uses two blend door actuators while the single zone system uses only one blend door actuator.
The A/C system is designed for the use of a non-CFC, R-134a refrigerant and uses an A/C evaporator to cool and dehumidify the incoming air prior to
blending it with the heated air. A temperature control determines the discharge air temperature by operating the blend door actuator(s), which moves the
blend-air door(s). This allows an almost immediate control of the output air temperature of the system. The mode door actuator operates the mode-air
doors which direct the flow of the conditioned air out the various air outlets, depending on the mode selected. The recirculation door actuator operates
the recirculation-air door which closes off the fresh air intake and recirculates the air already inside the vehicle. The electric door actuators are connected
to the vehicle electrical system by the HVAC wire harness. The blower motor controls the velocity of air flowing through the HVAC housing assembly
by spinning the blower wheel within the HVAC housings at the selected speed by use of the blower motor resistor.
The HVAC housing must be removed from the vehicle and disassembled for service of the heater core, A/C evaporator, evaporator temperature sensor,
blend-air and mode-air doors. The air inlet housing must be removed from HVAC housing and disassembled for service of the recirculation-air door.
