Ford 2003 Mustang Workshop Manual page 3069

Is the voltage reading greater than 10 volts?
C16 MEASURE THE RESISTANCE OF CIRCUIT 348 (VT)
Key in OFF position.
Disconnect: Function Selector Switch C294c.
Measure the resistance between the A/C function
selector switch C294c-1, circuit 348 (VT), harness side
and A/C cycling switch C130-4, circuit 348 (VT), harness
side.
Is the resistance reading less than 5 ohms?
C17 MEASURE THE VOLTAGE TO THE A/C PRESSURE
CUT-OFF SWITCH
Key in OFF position.
Connect: A/C Cycling Switch C130.
Disconnect: A/C Pressure Cut-off Switch C1078.
Turn the function selector switch to the A/C position.
NOTE: The A/C pressure cut-off switch C1078 for the
3.8L engine is shown, C1078 for the 4.6L engines is
similar. The pin locations and the circuits are identical.
Measure the voltage at the A/C high pressure cut-off
switch C1078-2 circuit 420 (DB/YE), harness side and
ground.
Yes
INSTALL a new function
selector switch. REFER to
Section 412-04 . TEST the
system for normal operation.
No
REPAIR circuit 348 (VT) for an
open. TEST the system for
normal operation.
Yes
GO to C19 .
No
GO to C18 .