Turn ignition switch ON (engine OFF). SUBARU alternator diagnostics Check if charge bulb comes on. NO Disconnect generator body harness connector. Turn ignition switch to "START". (engine starts.) YES Check if charge bulb comes on when terminal (L) of body harness connector is grounded. YES Check if charge bulb is OFF while engine idles. NO Measure VB of battery while running engine at 1,500 rpm. Check IC regulator. Check positive terminal of diode. YES (Remains ON or blinks.) VB is more than 15.5V. VB is less than 12.5V. Check IC regulator as a single unit. VB is more than or equal 12.5V, and VB is less than or equal to 15.5V. Turn light switch ON while engine idles. Terminal voltage NO Replace charge bulb. Check or replace fan belt. Check generator. Check S or BAT terminal for improper contact. Replace IC regulator assembly. NO Check if charge bulb comes on. No problems YES Check diode assembly.