Trouble Symptom:

WARNING: This page is about a different car, the 2002 Subaru Impreza. However, it is still accessible from the selected car via links, so may be relevant.

Radiator sub fan does not rotate under the above conditions.
Radiator sub fan does not rotate at high speed when the following conditions are both met:
1. Engine coolant temperature is above 90°C (194°F)
2. A/C is ON
  
  Fig 1: Radiator Sub Fan Switch Inspection (Turbo Model - Steps 1-7)
  Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Radiator Sub Fan Switch Inspection (Turbo Model - Steps 8-16)

Courtesy of SUBARU OF AMERICA, INC.

Fig 3: Radiator Sub Fan Switch Inspection (Turbo Model - Steps 17-24)

Courtesy of SUBARU OF AMERICA, INC.

Fig 4: Radiator Sub Fan Switch Inspection (Turbo Model - Steps 25-29)

Courtesy of SUBARU OF AMERICA, INC.