Possible Causes

WARNING: This page is about a different car, the 2003 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.

A short to voltage in circuit 15-Fa6 (GN/YE).
A/C clutch relay.
A/C compressor clutch/field coil.
DATC module.
PCM

Fig 1: Pinpoint Test M: A/C Is Always On (Steps M1-M6)

Courtesy of FORD MOTOR CO.

Fig 2: Pinpoint Test M: A/C Is Always On (Steps M7)

Courtesy of FORD MOTOR CO.