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Page 6
TG115A
Section C: Advanced Troubleshooting
Chart 1: No Alternator Output – Test Charging Circuit
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TEST MEASUREMENTS ARE TAKEN ON HARNESS PLUG AT ALTERNATOR. TAKING MEASUREMENTS FROM AN EX-
TENDED HARNESS PLUG MAY AFFECT RESULTS.
•
FOR REMOTE-MOUNTED REGULATOR, CHECK CONDITION OF HARNESS FUSES BEFORE TROUBLESHOOTING.
•
BEFORE STARTING DIAGNOSTIC SEQUENCE, VERIFY THE FOLLOWING AND REPAIR/REPLACE IF NOT TO SPEC:
−
BATTERIES FOR STATE-OF-CHARGE (25.0-28.0 V), CONDITION, AND SECURE CONNECTIONS.
−
MASTER BATTERY SWITCH FOR FUNCTION.
CAUTION
MAKE SURE METER PROBES DO NOT TOUCH OTHER PINS AND CAUSE AN ARC THAT MAY DAMAGE
PINS AND HARNESS WIRING.
How is the charging system energized?
Ignition (IGN)
Self-energized
Stop engine. Disconnect harness from alternator to regulator. If available, plug CEN A10-114 test tool into alternator
only. Otherwise carefully test directly through alternator harness pins. See Figures 6 and 7 on page 7 for reference.
1. Disconnect 5-pin connector from regulator before
starting engine.
2.
WITH ENGINE RUNNING:
test IGN circuit for battery
voltage from pin A
of vehicle
5-pin harness to alterna-
tor B‒ terminal. See Figure 8 on page 7 for reference.
3. Test for battery voltage from alternator B+ terminal to
alternator B‒ terminal.
4. Does battery voltage exist at both locations?
Yes
No
WITH ENGINE RUNNING:
Test for battery voltage
from alternator B+ terminal to alternator B‒ terminal.
Does battery voltage exist ?
No
Yes
Alternator is faulty.
Regulator is faulty.
System is operative.
Stop engine. Repair vehicle wiring as neces-
sary. Run engine and re-test charging circuit.
Is charging system performing properly?
No
Yes
Yes
MASTER BATTERY SWITCH ON, KEY ON, ENGINE OFF:
Alternator/regulator must pass all five tests.
1. Battery voltage test: Set DMM to DC Voltage test. Connect DMM red lead to pin D. Connect DMM black lead to pin
C. Battery voltage should exist.
2. Field coil resistance test: Set DMM on Ohms test. Field resistance between pin F and alternator B+ terminal should
measure nominal 1.0-1.5 ± 0.2 Ω. Field coil is defective if reading is less than 0.5 Ω or greater than 3 Ω.
3.
Field coil isolation test: Set DMM on Ohms test. Resistance between pins F and alternator B ‒ terminal should
measure OL.
4. Phase supply test: Set DMM to Diode test. Connect DMM black lead to pin B. Connect red lead to
alternator B+ terminal. DMM should read OL in this direction. Reverse leads. DMM should read diode voltage drop
in this direction. Repeat for pin B and B‒ terminal. Tests should read OL in one direction and diode voltage drop in
the other direction.
5. Temperature sensor test: Set DMM to Ohms test. Resistance between pin E and alternator B- terminal should
measure between 60 kΩ and 130 kΩ at room temperature.
No
