FORD MUSTANG 2003 Workshop Manual

If two substances of different temperature are placed near each other, the heat in the warmer
substance will transfer to the colder substance.
Latent Heat of Vaporization
When a liquid boils (converts to a gas), it absorbs heat without raising the temperature of the resulting
gas. When the gas condenses (reverts back to a liquid), it gives off heat without lowering the
temperature of the resulting liquid.
Relative Humidity
The amount of moisture (water vapor content) that the air can hold is directly related to the air
temperature. The more heat there is in the air, the more moisture the air can hold. The lower the
moisture content in the air, the more comfortable you feel. Removing moisture from the air lowers its
relative humidity and improves personal comfort.
Effects of Pressure on Boiling or Condensation
As the pressure is increased on a liquid, the temperature at which the liquid boils (converts to a gas)
also increases. Conversely, when the pressure on a liquid is reduced, its boiling point is also reduced.
When in the gas state, an increase in pressure causes an increase in temperature, while a decrease in
pressure will decrease the temperature of the gas.
Compressor Anti-
Slugging Strategy
Liquid refrigerant may accumulate in the A/C compressor under certain conditions. To alleviate
damage to the A/C compressor, compressor anti- slugging strategy (CASS) is utilized.
CASS is initiated only under specific conditions:
zthe ignition is off for more than 8 hours
z the ambient temperature is above -4º C (25ºF)
z battery voltage is above 8.5 volts during engine cranking
When these conditions are present, the powertrain control module (PCM) will activate the A/C control
relay prior to cranking of the engine. The A/C control relay engages the A/C compressor for
approximately 4- 15 A/C compressor revolutions or a maximum of 2 seconds (depending upon vehicle
application), allowing the liquid refrigerant to be pushed from the A/C compressor. CASS is initiated by
the PCM regardless of the function selector switch position or the EATC system settings.
The Refrigerant Cycle
During stabilized conditions (air conditioning system shut down), the refrigerant is in a vaporized state
and pressures are equal throughout the system. When the A/C compressor (19703) is in operation, it
increases pressure on the refrigerant vapor, raising its temperature. The high- pressure and high-
temperature vapor is then released into the top of the A/C condenser core (19712).
The A/C condenser core, being close to ambient temperature, causes the refrigerant vapor to
condense into a liquid when heat is removed from the refrigerant by ambient air passing over the fins
and tubing. The now liquid refrigerant, still at high pressure, exits from the bottom of the A/C
condenser core and enters the inlet side of the A/C evaporator core orifice (19D990).
The A/C evaporator core orifice is the restriction in the refrigerant system that creates the high
pressure buildup upstream of the A/C evaporator core (19860) and separates the high and low
pressure sides of the A/C system. As the liquid refrigerant leaves this restriction, its pressure and
boiling point are reduced.
The liquid refrigerant is now at its lowest pressure and temperature. As it passes through the A/C Klj . 3 ba
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evaporator core, it absorbs heat from the passenger compartment airflow passing over the plate/fin
sections of the A/C evaporator core. This addition of heat causes the refrigerant to boil (convert to a
gas). The now cooler passenger compartment air can no longer support the same humidity level of the
warmer air and this excess moisture condenses on the exterior of the evaporator coils and fins and
drains outside the vehicle.
The suction accumulator/drier (19C836) is designed to remove moisture from the refrigerant and to
prevent any liquid refrigerant that may not have been vaporized in the A/C evaporator core from
reaching the A/C compressor. The A/C compressor is designed to pump refrigerant vapor only, as
liquid refrigerant will not compress and can damage the A/C compressor.
The refrigerant cycle is now repeated with the A/C compressor again increasing the pressure and
temperature of the refrigerant.
The A/C cycling switch (19E561) interrupts compressor operation before the external temperature of
the A/C evaporator core gets low enough to cause the condensed water vapor (excess humidity) to
turn to ice. It does this by monitoring low side line pressure. It is known that a refrigerant pressure of
approximately 210 kPa (30 psi) will yield an operating temperature of 0°C (32°F). The A/C cycling
switch controls system operation in an effort to maintain this temperature.
The high side line pressure is also monitored so that the A/C compressor operation can be interrupted
if system pressure becomes too high.
The A/C compressor pressure relief valve (19D644) will open and vent refrigerant to relieve unusually
high system pressure.
Clutch Cycling Orifice Tube Type Refrigerant System Klj . 4 ba
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Item Part Number Description
1 19D701 A/C charge valve port (low side)
2 19E561 A/C cycling switch
3 19C836 Suction accumulator/drier
4 19703 A/C compressor
5 19D644 A/C compressor pressure relief valve
6 19D594 A/C pressure cutoff switch
7 19D701 A/C charge valve port (high side)
8 19712 A/C condenser core Klj . 5 ba
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System Air Flow Description
MAX A/C
When MAX A/C is selected:
zThe air inlet door vacuum control motor is at full vacuum, closing off outside air and admitting
only recirculated air.
z The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum
control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small
amount of airflow from the side window demisters will be present.
z Blended air temperature is available.
z The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
z The blower motor is on.
NORM A/C
When NORM A/C is selected:
zThe air inlet door vacuum control motor is at no vacuum, admitting only outside air into the
passenger compartment. 9 19D990 A/C evaporator core orifice
10 19860 A/C evaporator core
11 — Low pressure vapor
12 — High pressure vapor
13 — Low pressure liquid
14 — High pressure liquid Klj . 6 ba
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z
The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum
control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small
amount of airflow from the side window demisters will be present.
z Blended air temperature is available.
z The A/C compressor will operate if the outside air temperature is above approximately 6°C (43°
F).
z The blower motor is on.
PANEL
When PANEL is selected:
zThe air inlet door vacuum control motor is at no vacuum, admitting only outside air into the
passenger compartment.
z The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum
control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small
amount of airflow from the side window demisters will be present.
z The temperature can be adjusted to heat the air, but the air cannot be cooled below the outside
temperature.
z The A/C compressor will not operate.
z The blower motor is on.
OFF
When OFF is selected:
zThe air inlet door vacuum control motor is at full vacuum, closing off outside air from entering
the passenger compartment.
z The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum Klj . 7 ba
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control motor is at no vacuum, closing off airflow to the defrost duct, side window demisters,
floor duct and instrument panel A/C registers.
z The A/C compressor will not operate.
z The blower motor is off.
FLOOR
When FLOOR is selected:
zThe air inlet door vacuum control motor is at no vacuum, admitting only outside air into the
passenger compartment.
z The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum
control motor is at no vacuum, directing airflow to the floor duct. A small amount of airflow from
the side window demisters will be present.
z The temperature can be adjusted to heat the air, but the air cannot be cooled below the outside
temperature.
z The A/C compressor will not operate.
z The blower motor is on.
FLOOR/DEFROST
When FLOOR/DEFROST is selected:
zThe air inlet door vacuum control motor is at no vacuum, admitting only outside air into the
passenger compartment.
z The panel/floor door vacuum control motor is at partial vacuum and the panel/defrost door
vacuum control motor is at no vacuum, directing airflow to the floor duct, the defroster duct, and
the side window demisters.
z The temperature can be adjusted to heat or cool the air below the outside temperature. Klj . 8 ba
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z
The A/C compressor will operate if the outside air temperature is above approximately 6°C (43°
F).
z The blower motor is on.
DEFROST
When DEFROST is selected:
zThe air inlet door vacuum control motor is at no vacuum, admitting only outside air into the
passenger compartment.
z The panel/floor door and panel/defrost door vacuum control motors are at no vacuum, directing
airflow to the defroster duct and the side window demisters.
z The temperature can be adjusted to heat or cool the air below the outside temperature.
z The A/C compressor will operate if the outside air temperature is above approximately 6°C (43°
F).
z The blower motor is on. Electrical Components Klj . 9 ba
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Item Part Number Description
1 19980 Manual A/C control assembly
2 19E561 A/C cycling switch
3 19D594 A/C pressure cutoff switch (V6)
4 19D594 A/C pressure cutoff switch (V8)
5 12A650 Powertrain control module
6 12B581 Constant control relay module
7 19703 A/C compressor
8 19805 Blower motor Klj . 10 ba
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9 18591 Heater blower motor resistor Klj . 11 ba
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DIAGNOSIS AND TESTING
Climate Control System
Refer to Wiring Diagrams Cell
54 , Air Conditioner/Heater for schematic and connector information.
SECTION 412-
00: Climate Control System - General Information 2003 Mustang Workshop Manual Special Tool(s)
Connector, Refrigerant
Pressure Line
412-
093 (T94P-19623- E) Set, A/C Fittings
412-
DS028 (014- 00333, D93L-
19703- B) or equivalent Vacuum Pump Kit
416-
D002 (D95L-7559- A) or
equivalent Breakout Box, EEC-V Control
System
418- 049 (014-00950, T94L-50-
EEC- V) Worldwide Diagnostic System
(WDS)
418-
F224,
New Generation STAR (NGS)
Tester
418- F052, or equivalent
diagnostic tool Pressure Test Kit
014-
R1072 or equivalent 77 III Automotive Meter
105-
R0056 or equivalent Klj . 1 ba
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