C.E. Niehoff & Co. N1246-1 Troubleshooting Guides - Manual (Page 6)

Page 6
TG0049A
(CONT’D)
Section 3: Advanced Troubleshooting
Yes No
Alternator is defective.
Unplug alternator-to-regulator harness from regulator. Connect red lead from DMM to socket A in plug.
Connect black lead to socket D in plug. Does resistance read 1.8 ± 2.2 ohms?
Chart 3b – No 28 V Alternator Output – Test OVCO Circuit
Yes No
Replace existing regulator with known good regulator.
Run engine. Does OVCO trip?
Alternator is defective.
T T
Chart 3a – No 14 V Alternator Output – Test OVCO Circuit
Yes No
With red lead from DMM connected to socket A in plug, connect black lead to B– terminal. Does
resistance read OL (out of limits)?
Alternator is defective.
T
Chart 3 – OVCO Trip – Determine 28 V or 14 V
Yes No
28 V side tripped OVCO circuit.
Go to Chart 3b.
With meter red lead on 28 V B+ at battery and black lead on chassis ground, start engine.
Watch meter dial: Does meter read charge voltage above 29 V?
T
14 V side tripped OVCO circuit.
Go to Chart 3a.
T
T
T
T
Figure 5 – Alternator-to-Regulator Harness Plug
Yes No
Original regulator
is defective.
Replace regulator with known good regulator.
Run engine. Does OVCO trip?
Alternator
is defective.
T T
Yes No
Unplug alternator-to-regulator harness from regulator. At receptacle on regulator, connect red lead from DMM
to socket G. Connect black lead to B– terminal. Does resistance read OL (out of limits)?
T T
SOCKET CONNECTIONS
A ° F–
B ° AC1
C ° Not used
D ° B+
E ° P
F ° AC2
G ° B–
H ° B–
I ° AC3
Alternator is defective.
Original regulator
is defective.