Page 5
TG0060A
Section C: Advanced Troubleshooting
Figure 4 – Alternator-to-Regulator Harness Plug
PIN CONNECTIONS
Pin A
F–
Pin B
Phase
Pin C
GND
Pin D
B+
Pin E
Not used
Chart 1 –
No Alternator Output –
Quick Diagnostic
With engine running: Does battery voltage exist at alternator B+ terminal and regulator IGN terminal?
Yes
No
Repair vehicle harness circuit to IGN terminal on
regulator or B+ terminal on alternator.
With key off, engine off: Unplug alternator-to-regulator harness. Connect DMM on DC volt scale across
pins C and D. Does battery voltage exist?
Yes
No
With DMM on resistance scale, does the field resistance between pin A in harness plug and
alternator B+ terminal measure about 1.0 (±0.2) ohms?
Yes
No
Alternator is defective.
Alternator is defective.
With key off, engine off: Does battery voltage exist at alternator B+ terminal?
Yes
No
Repair vehicle harness circuit to B+ terminal on alternator.
With key on, engine off: Momentarily (1 sec.) jumper pin A in
harness plug to alternator B– terminal. Touch shaft with steel
tool to detect significant magnetism. Is shaft magnetized?
Yes
No
Alternator is defective.
Regulator is defective.
Set DMM to diode test.
Check negative diodes: Connect red lead to pin B in harness plug. Connect black lead to alternator B–
terminal. Meter should read OL (over limit). Reverse leads. Meter should read voltage drop.
Check positive diodes: Connect red lead to pin B in harness plug. Connect black lead to alternator B+
terminal. Meter should read voltage drop. Reverse leads. Meter should read OL (over limit).
Yes
No
Alternator is defective.
Remote-mounted regulator applications:
Check condition of fuse in wiring harness before troubleshooting.
If you have questions about your alternator or any of these test procedures, or if you need to locate a Factory Authorized Service Dealer, please contact us at:
C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA
TEL: (800) 643–4633 USA and Canada • TEL: (847) 866–6030 outside USA and Canada • FAX: (847) 492–1242
Email:
D
A
B
C
E
When conducting this step, ensure that the probes do not touch other pins, as an arc may
damage the wiring in the harness.
CAUTION
