A/C—Heater System, Manual

The manual A/C-heater system has the following features:

• It is a fixed A/C evaporator core orifice cycling A/C clutch-type system.
• It uses a suction accumulator/drier (19C836).
• It also incorporates a multi-pass, S-flow A/C evaporator core (19860) .
• There are two service access gauge port valves which are Schrader-type valves.
• The A/C compressor pressure relief valve (19D644) is located in the A/C compressor to condenser discharge line (19972) near the A/C compressor (19703) .
• A special adapter is required to connect a manifold gauge set to the valve.
• The low-pressure valve is located in the suction line.
• The refrigerant system uses FS-10 A/C compressors for all engine applications.

The manual A/C-Heater system operates as follows:

• System airflow is controlled by a six-port vacuum selector valve which is integral with the control assembly.
• System air temperature is regulated by a A/C air temperature control door operated by a new pull-pull cable.
• The heater blower motor electrical circuit uses ground side switching.
• The switch (19986) and the heater blower motor switch resistor (18591) are on the ground side of the motor instead of the battery side. This protects the heater blower motor switch resistor from overheating in the event of an electrical short.
• During system operation, air is drawn directly into the system by the A/C blower motor and A/C blower wheel (19834) from the cowl air intake in all function selector knob (18519) settings except OFF and MAX A/C.
  • In the MAX A/C position, airflow is from inside the vehicle through the A/C recirculating air duct.
• The air is then forced by the blower through the A/C evaporator core and, depending on the setting of the temperature knob , through and/or around the heater core (18476) into the heater air plenum chamber (18471).
• Air is then directed to the floor, windshield defroster hose nozzles (18490) , A/C side window demister and hoses (19E630) or the instrument panel A/C register (19893) depending on the position of the function selector knob .
• Airflow volume through the system is controlled by a four-position blower motor 18C535.The blower motor 18C535 used in conjunction with the resistor assembly, provides four speeds to control airflow.

Refer to the A/C-heater system airflow schematic and Vacuum Control Chart. These charts show the possible airflow routes and door positions. The vacuum control chart gives the vacuum applications for the different positions of the function and temperature selector knobs .