Primary Manual Air Conditioning Vacuum System

The front manual air conditioning system uses vacuum to operate the air valves (doors) that control airflow through the air conditioning module.

Vacuum is supplied from the vacuum tank suspended from the hood inner panel. Just ahead of the air conditioning control assembly in the instrument panel, the vacuum supply line divides into two branches. One branch brings vacuum to an on-off vacuum valve on the control assembly. When the control assembly temperature lever is in the full COLD position, the vacuum valve is open and vacuum is supplied to a hot water bypass valve i the lower RH corner of the engine compartment. This causes hot water to bypass the air conditioning system heater core to prevent unwanted heat from reducing the cooling effect of the system. When the temperature lever is moved away from the full COLD position, bypass valve vacuum is vented and bypass valve permits hot water to reach the heater core.

The other branch of the vacuum supply line brings vacuum to the rotary selector valve that is operated by the mode lever of the control assembly. A vacuum hose harness brings vacuum from the ports in the rotary selector valve to the vacuum actuators for the air valves of the air conditioning system. All actuators except the heater-defroster are two position actuators controlled by one vacuum hose. The heater-defroster actuator is a three position device controlled by two vacuum hoses.

Air Distribution:

Rotary Selector Valve Operation Chart:

Application of vacuum or vented air to each actuator is determined by the operating mode selected by setting the mode lever in the control assembly. The charts indicate the air outlets that operate in each mode selection and the response of the rotary selector valve to each mode lever position.