C.E. Niehoff & Co. C651/C654 Troubleshooting Guides User Manual
Page 7
Page 7
TG0010C
Test for battery voltage at both alternator 28 V and 14 V B+ terminals. Does
battery voltage exist at both terminals?
Yes
No
Repair vehicle wiring as necessary. Continue test.
Run engine and re-test charging circuit for operation.
Chart 4 – No Alternator Output – Test Charging Circuit
Jumper 28 V B+ terminal on alternator to E terminal on regulator. Run engine. Does alternator charge?
Yes
No
Turn off engine, leave key on. Remove jumper wire. Go to
E terminal on regulator. Test for battery voltage going into
E terminal from battery. Does battery voltage exist?
Yes
No
STATIC TEST – ENGINE OFF, BATTERY SWITCH ON, KEY ON
Repair vehicle circuit to E terminal.
Vehicle charging circuit test is
complete.
Figure 5 – Alternator-to-Regulator Harness Plug
PIN CONNECTIONS
Pin A
F–
Pin B
SCR Gate
Pin C
B–
Pin D
28 V B+
Pin E
14V B+
Pin F
F+
Pin G
AC Signal
Pin H
Not Used
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Yes
Turn off engine, leave key on. Connect jumper
wire from pin F in harness plug to 28 V B+
terminal on alternator. Does spark occur?
Disconnect jumper wires. Connect DMM red
lead to pin D in alternator-to-regulator harness
plug. Connect black lead to pin C in same plug.
Does 24 V battery voltage exist?
Yes
No
Alternator is
defective.
No
Alternator is defective.
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Connect DMM red lead to pin E in alternator-
to-regulator harness plug. Connect black lead
to pin C in same plug. Does 12 V battery voltage
exist?
Yes
No
Alternator is
defective.
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Regulator is
defective.
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Section 3: Advanced Troubleshooting
Yes
With previous jumper still in place, connect
another jumper wire from pin A in harness plug
to B– terminal on alternator. Spark will occur.
Touch steel tool to shaft to detect significant
magnetism. Is shaft magnetized?
No
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Alternator is defective.
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