C.E. Niehoff & Co. N1610 Troubleshooting Guides - Manual (Page 5)

Page 5 TG61B
Shut off engine. With key off, engine off: Test for battery voltage at alternator 28 V B+
terminal. Does battery voltage exist?
Yes No
Repair vehicle ignition circuit wiring as necessary. Continue test.
Chart 1 — No 28V Alternator Output – Test Charging Circuit
With DMM, check resistance across field coil. Connect red lead of DMM to socket C in alternator-to-regulator
harness plug. Connect black lead to B+ terminal on alternator. Does meter show 1.5 ± 0.2 ohms?
Yes No
STATIC TEST – KEY ON, ENGINE OFF


Yes
Test phase signal into regulator (AC). Set meter to diode tester:
Connect red lead of DMM to socket A of regulator harness and
black lead to socket B. Meter should show voltage drop value.
Then reverse meter lead connections. Meter should show OL
(blocking).
No


Shut down vehicle and restart engine. Does alternator function normally after restart?
Yes No


Figure 3 – Alternator-to-Regulator
7-Socket Harness Plug
With key on, engine running: Test for battery voltage between IGN terminal on regulator and alternator B–
terminal. Does 28 V battery voltage exist?
Yes No
 

With key off, engine off: Remove alternator-to-regulator 7-pin harness from regulator. Test for battery
voltage across sockets A and D in harness plug. Does 28 V battery voltage exist?
Alternator is defective.

Alternator is
defective.

Alternator is defective.

Regulator is defective.
A
B
C
D
E
F
G
Yes
Connect jumper wire from socket C in regulator harness plug to B– terminal on
alternator and momentarily (1 sec.) jump pin F to B+. Spark will occur. Touch
steel tool to shaft to detect significant magnetism. Is shaft magnetized?
No


Repair vehicle ignition circuit wiring as necessary. Continue test.
Yes No
 
Section C: Advanced Troubleshooting
(CONT’D)
Regulator responded to overvoltage condition.
Go to Chart 3 on page 6 to troubleshoot OVCO.
SOCKET CONNECTIONS
IN ALTERNATOR PLUG
A  B−
B  AC
C  F−
D  B+
E  TS
F  F+
G  Not used