Ford 2003 Mustang Workshop Manual page 3064

Is the heater core inlet hose too hot to handle?
B3 CHECK THE ENGINE COOLING SYSTEM INCLUDING
RADIATOR CAP FOR LEAKS
Fill the engine cooling system to specified level.
NOTE: It is not necessary to check the components
separately at this time.
Pressure check the engine cooling system. Refer to
303-03A or Section 303-03B
Does the engine cooling system, including the radiator
cap, hold pressure?
B4 CHECK THE HEATER CORE OUTLET HOSE FOR HOT
WATER
Feel the heater core outlet hose.
Is the heater core outlet hose cool or cold?
PINPOINT TEST C: THE A/C DOES NOT OPERATE/DOES NOT
OPERATE CORRECTLY
C1 CHECK THE PCM PID WACF
Connect the diagnostic tool.
Turn the function selector to the OFF position.
Key in ON position.
Enter the following diagnostic mode on the diagnostic
tool:
Monitor the PCM PID WACF while turning the function
selector.
Does the PCM PID WACF read YES?
C2 CHECK THE PCM PID WACF WITH THE A/C ON
Turn the function selector switch to the A/C position.
Enter the following diagnostic mode on the diagnostic
.
Test Step
Yes
GO to B4 .
No
Section
Pressure test the heater
core. REFER to
Component Tests, Heater
Core — Pressure Test.
Yes
TEST the heater core for a
plugged or partially
plugged condition. REFER
to Section 303-03A
Section 303-03B
No
GO to Pinpoint Test E
Result / Action to Take
Yes
REFER to the Powertrain
Control/Emissions Diagnosis
(PC/ED) manual.
No
GO to C2 .
Yes
REFER to the Powertrain
or
.
.