C.E. Niehoff & Co. N1313 Troubleshooting Guides - Manual (Page 7)

Page 7
TG16F
Section C: Advanced Troubleshooting
(CONT’D)
Yes No
Alternator is defective.
Unplug alternator-to-regulator 5-pin harness from regulator. Connect red lead from DMM to pin A in plug. Connect
black lead to pin D in plug. Does resistance read 1.0 ± 0.2 ohms?
Chart 3b – No 28 V Alternator Output – Test OVCO Circuit (28 V LED on N3222 steady RED)
Yes No
Replace existing regulator with known good regulator.
Run engine. Does OVCO trip?
Alternator is defective. Original regulator is
defective.
 
Yes No
Original regulator
is defective.
Replace regulator with known good regulator. Run
engine. Does OVCO trip?
Chart 3a – No 14 V Alternator Output – Test OVCO Circuit (14 V LED on N3222 steady RED)
Alternator is defective.
 
Yes No
Set DMM to  auto-ranging scale. Connect red lead from DMM to pin A in plug. Connect black lead
to B– terminal. Does resistance read OL (out of limits)? Then connect red lead to pin D and black lead
to B– terminal. Does resistance read OL (out of limits)?
Alternator is defective.

Yes No
Alternator is defective.
Disconnect alternator-to-regulator 3-pin harness from regulator. At receptacle on regulator, connect red lead from
DMM to pin C. Connect black lead to B– terminal. Does resistance read OL (out of limits)?

Figure 5 – Alternator-to-Regulator 3-Pin Harness Receptacle
PIN CONNECTIONS
A 14 V B+
B unused
C 14 V Control
Chart 3 – OVCO Trip N3039 only – Determine 28 V or 14 V (LEDs on N3222 will determine which output)
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 battery charge above 29 V?

14 V side tripped OVCO circuit.
Go to Chart 3a.


Figure 6 – Alternator-to-Regulator 5-Pin Harness Plug
PIN CONNECTIONS
A
F–
B unused
C B–
D 28 V B+
E Phase


A
B
C
