Ford 2003 Mustang Workshop Manual page 3061

Does the vacuum drop?
A13 REVIEW THE VEHICLE'S HISTORY
Key in OFF position.
Review the vehicles history.
Did the climate control system function correctly prior to
this concern?
A14 CHECK THE VACUUM HOSES TO DAMPER DOORS
Connect a vacuum pump to each hose and try to pull a vacuum.
If the vacuum pump can pull a vacuum, the hose is plugged. If
the vacuum pump pulls a partial vacuum, the hose is restricted.
Is a hose plugged or restricted?
A15 CHECK THE VACUUM HARNESS
Compare the vacuum hose color in each vacuum harness to the
vacuum diagram.
Does the hose color agree with the schematics?
A16 CHECK A/C VACUUM CIRCUIT
Check the A/C vacuum circuit for pinched or kinked vacuum
hose.
system for normal
operation.
No
REPAIR or INSTALL a
new function selector
switch. TEST the
system for normal
operation.
Yes
GO to A16 .
No
GO to A14 .
Yes
INSTALL a new
vacuum hose. TEST
the system for normal
operation.
No
GO to A15 .
Yes
GO to A16 .
No
INSTALL a new
vacuum harness. TEST
the system for normal
operation.
Yes
REPAIR or INSTALL a
new vacuum hose.
TEST the system for
normal operation.
No
GO to A17 .