Quick diagnostic – C.E. Niehoff & Co. N1240-3/N1243-2 Troubleshooting Guides User Manual
Page 5
Page 5
TG0040A
Section 4: Advanced Troubleshooting
Figure 4 – Alternator-to-Regulator Harness Plug
PIN CONNECTIONS
Pin A
F–
Pin B
Phase 1
Pin C
GND/B–
Pin D
B+
Pin E
Kelvin –
Pin F
F+
Pin G
Kelvin +
Pin H
Phase 2
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.
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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 pins F and A in harness plug measure about
1.4 (±0.2) ohms?
Yes
No
Alternator is defective.
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Alternator is defective.
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With key off, engine off: Does battery voltage exist at alternator B+ terminal?
Yes
No
Repair vehicle harness circuit to B+ terminal on alternator.
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Set DMM to diode test. Check continuity of thermal switch and rear stator diodes: Connect red lead to pin B
in harness plug. Connect black lead to alternator B+ terminal. Meter should read one diode drop (approx.
0.6 to 0.9 V). Disconnect leads. Connect red lead to alternator B– terminal. Connect black lead to pin B.
Meter should read one diode drop (approx. 0.6 to 0.9 V).
Yes
No
Alternator is defective.
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Set DMM to diode test. Check continuity of front stator diodes: Connect red lead to pin H in harness plug.
Connect black lead to alternator B+ terminal. Meter should read one diode drop (approx. 0.6 to 0.9 V).
Disconnect leads. Connect red lead to alternator B– terminal. Connect black lead to pin H. Meter should read
one diode drop (approx. 0.6 to 0.9 V).
Yes
No
Alternator is defective.
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Go to Page 6 to continue.