Subaru XT 1988 Service Manual page 1210

I
ENGINE ELECTRICAL SYSTEM
BATTERY OVERCHARGES
Check terminal-B voltage while increasing engine
speed from idle slowly; check if terminal-B voltage
builds up above 15.0V
I
YES
NO
Check if terminal-F voltage is higher at 3,000 rpm
than at idle
YES
*1
After idling 2 or 3 minutes (more than 5 minutes
when battery is discharged), increase engine speed
to 2,500 rpm and check terminal-L voltage to see
if it is regulation voltage (14.0 to 15.0V)
YES
Normal
*2
Terminal-F grounded?
NO
Ground terminal F
NO
Replace IC regulator
NO
I C alternator defective
*1 When checking this, be sure to turn off the lights and all other electrical loads.
6-1
OK
Replace.IC regulator
*2 To check the voltage at terminal F, insert the contact bar straight through the access hole. This will allow the contact bar
to hit only terminal F. Even if the bar comes into contact with the rear bracket during insertion, no damage will result
as long as it is released.
Fig. 68
29