C.E. Niehoff & Co. N1128 Troubleshooting Guides - Manual (Page 7)

Page 7
TG0027A
(CONT’D)
Section 4: Advanced Troubleshooting
Chart 2 – 14 V LED Solid AMBER – No 14 V Alternator Output – Test Circuit
Figure 5 – Phase Connection 3-Pin Harness Plug
PIN CONNECTIONS
A Phase P1
B Phase P2
C Phase P3
With key off, engine off: Test for battery voltage of 14 V output terminal on regulator.
Does +14 V battery voltage exist?
Yes No
T T T T T
T T T T T
Yes
Set DMM to diode tester. Connect red lead of DMM to socket C of regula-
tor harness plug and black lead to each phase pin in phase harness
plug. Meter should show voltage drop value.
Then reverse meter lead connections. Meter should show OL (blocking).
No
T T T T T
Alternator is defective.
T T T T T
Regulator is defective.
Figure 4 – Alternator-to-Regulator 4-Socket Harness
Plug
SOCKET CONNECTIONS
A F–
B Phase Signal AC
C B–
D 28 V B+
Check and repair wiring and battery cables as necessary.
Continue test.