No-Load Test
WARNING: This page is about a different car, the 2004 Subaru Forester, 2003 Subaru Forester, and 2002 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
With switch ON, adjust the variable resistance to obtain 11 volts, take the ammeter reading, and then measure the starter speed. Compare the values.