Housing Assembly HVAC: Description and Operation
HVAC HOUSINGDESCRIPTION
HVAC Housing - LHD Shown, RHD Similar:
Both the single zone manual temperature control (MTC) heating-A/C system and the heater-only system are equipped with a common HVAC housing assembly that combines A/C and heating capabilities into a single unit located within the passenger compartment. The HVAC housing assembly consists of the following:
- HVAC housing - The HVAC housing consists of an upper housing and a lower housing that are attached together by screws and clips and is mounted to the dash panel behind the instrument panel. The HVAC housing contains the heater core, A/C evaporator, blend-air and mode-air doors, and has mounting provisions for the air-door actuators, floor distribution duct, blower motor, blower motor resistor, blower motor relay and the HVAC wire harness and vacuum harness.
- Air inlet housing - The air inlet housing 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 and its linkage.
The heating-A/C system is a blend-air type system. The blend-air door controls the amount of conditioned air that is allowed to flow through, or around, the heater core.
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, which moves the blend-air door. This allows an almost immediate control of the output air temperature of the system. The two mode door actuators operate 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 recirculation door actuator is connected to the vehicle electrical system by the HVAC wire harness and, the recirculation door actuator and mode door actuators are connected to the A/C-heater control by the HVAC vacuum harness. The blower motor controls the velocity of air flowing through the HVAC housing assembly by spinning the blower wheel within the HVAC housing 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, 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.