Heater And Air Conditioner
HEATER AND AIR CONDITIONER
Outside fresh air enters the vehicle through the cowl top opening at the base of the windshield (1), and passes through a plenum chamber to the HVAC housing. Air flow can then be adjusted by the blower motor (2) speed switch on the A/C Heater Control Panel. The fresh air then travels through the evaporator (6) and the heater core (5) then out into the vehicle through the side and floor vents (3-4).
It is also important to keep the air intake openings clear of debris because leaf particles and other debris that is small enough to pass through the cowl plenum screen can accumulate within the HVAC housing. This closed, warm, damp and dark environment created within the HVAC housing is ideal for the growth of certain molds, mildews and other fungi. Any accumulation of decaying plant matter provides an additional food source for fungal spores, which can enter the housing with the fresh air. Excess debris, as well as objectionable odors created by decaying plant matter and growing fungi can be discharged into the passenger compartment during HVAC system operation.
AIR CONDITIONING
The A/C Compressor (8) is driven by the engines accessory drive belt. The A/C compressor (8) compresses the gaseous refrigerant (7) which heats up and flows into the condenser (6). The heat resulting from the compression is absorbed from the refrigerant by the surface of the condenser (6). As the refrigerant cools down it liquefies becoming a high-pressure liquid (4). As the refrigerant (4) flows through the receiver/drier (5) it is purified of chemical and mechanical impurities. It then travels to the expansion valve (3) which sprays the cooled, low pressure liquid (4) into the evaporator (1), located in the fresh air flow. The refrigerant (4) evaporates in the evaporator (1). This evaporation process absorbs heat from the fresh air flowing across the system of tubes and honeycombs, therefore cooling the air that is blown into the passenger compartment. The low pressure gas then returns to the A/C compressor.
The moisture in the fresh air is condensed out and the condensation drained to the outside through a drain in the HVAC housing. The air is dried. The A/C compressor sucks in the refrigerant which has become gaseous due to the absorption of heat and compresses it again. When the engine is running and with blower switched on, cooled air can flow into the passenger compartment through various outlet openings. The intensity of cooling depends on the passenger compartment temperature set and the blower output.
The mode control on the A/C Heater Control Panel is used to direct the conditioned air to the selected system outlets. The mode control switches directs engine vacuum to control the mode doors, which are operated by vacuum actuators. The mode control switches electrical current to control the mode doors, which are operated by actuators.
- Mode Control (1)
- Passenger Temperature Control (2)
- Air Conditioning Button (3)
- REST Button (4)
- Driver's Temperature Control (5)
- Fan Control (6)
- Rear Defogger Button (7)
HEATER SYSTEM
The Water Pump (7) pumps coolant through the engine (3). There the coolant absorbs heat from the engine (3), heating up the coolant. Then the heated coolant flows through into the Heater Core (4) where the heat is transferred to the air in the passenger compartment. The coolant flowing through the Heater Core (4) is controlled by a Coolant Circulation Valve (6) located in the coolant return. The coolant can be controlled separately for the left and right sides.
The coolant returns to the Water Pump (7) via the coolant return hose. A Coolant Circulation Pump (5) is installed between the Coolant Circulation Valve (6) and the Water Pump (7). The Coolant Circulation Pump (5) serves for maintaining a uniform flow of heating water through the Heater Core (4) even at low engine speeds and in the Residual Engine Heat Utilization (REST) mode . The major portion of the coolant flows from the engine (3) to the Thermostat (2) instead of flowing through the Heater Core (4). The Thermostat (2) routes the water through the radiator (8) or directly to the Water Pump (7) depending on the temperature.
In a blend-air system, a Blend Door controls the amount of unconditioned air (or cooled air from the Evaporator) that is allowed to flow through, or around, the Heater Core (3). A temperature control knob on the A/C Heater Control Panel determines the discharge air temperature by energizing the Blend Door Actuator, which operates the Blend Door. This allows an almost immediate control of the output air temperature of the system.
R.E.S.T. SYSTEM
The Coolant Circulation Pump pumps the heated coolant to the Heater Core when the engine is off. When the REST button (4) is pressed the temperature is controlled by the A/C Heater Control Module (in the same manner as when the Ignition is ON). The A/C Heater Control module switches the Coolant Circulation Pump on which drives the impeller via a magnetic clutch. A light in the switch will illuminate indicating that the REST system is active.