Fig. 2: Identifying A/C
-Heater Air Distribution Components
Courtesy of FORD MOTOR CO.
OPERATION
A/C-HEATER CONTROL PANEL
The A/C-heater panel is located in the center of instrument panel above the radio. Air discharge outlets are located above, below, in center
and on both sides of instrument panel. The climate control panel consists of 3 slide levers, one A/C on-off push button and a rotary blower
switch.
The lower slide lever is used to control temperature. Sliding lever from far left side (cool) to far right side (warm) increases interior
temperature. The middle slide lever selects fresh air from outside or recirculated air from inside. The upper slide lever controls air delivery
mode. A/C push-button on-off switch activates air conditioning system.
THERMOSTATIC SW ITCH
With A/C system operating, thermostatic switch determines A/C compressor clutch on-time. Control is accomplished by a cable attached
between the temperature blend lever and thermostatic switch. The thermostatic switch sensing tube is installed into (or near) evaporator fins.
Switch is wired in series with A/C relay and Electronic Control Assembly (ECA). The ECA calculates compressor on-time based on A/C relay
signals. This controls evaporator temperature to regulate cool air entering vehicle.
THERMOSTATIC EXPANSION VALVE
The Thermostatic Expansion Valve (TXV) is a controlling device metering liquid refrigerant from high pressure line into evaporator. It also
provides for complete vaporization of all refrigerant entering evaporator.
The high refrigerant pressure is reduced before entering evaporator by a ball valve within TXV. Depending on pressure applied to TXV
diaphragm from both sides of system, TXV allows more or less high pressure refrigerant to be discharged through its orifice into evaporator.
See Fig. 3
.
Page 2 of 14 MITCHELL 1 ARTICLE - 1991 AIR CONDITIONING & HEAT MANUAL A/C
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