C.E. Niehoff & Co. N1245/N1248-3 Troubleshooting Guides - Manual (Page 7)

Page 7 TG44D
Section C: Advanced Troubleshooting
(CONT’D)
Shut off engine. With key off, engine off: Test for battery voltage at alternator 28 V B+
terminal. Does battery voltage exist?
Yes No
Chart 2 – No Alternator Output – N3044 or N3261 Regulator
With DMM, check resistance across field coil. Connect red lead of DMM to socket A in alternator-to-regulator har-
ness plug. Connect black lead to socket B in plug. Does meter show 1.5 ± 0.2 ohms?
Yes No


Yes
Test phase signal going into regulator (AC). Set meter to diode tester:
Connect red lead of DMM to socket C of alternator-to-regulator
harness plug and black lead to socket E of plug. 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 7 – Alternator-to-Regulator
Harness Plug
With key on, engine running: Test for battery voltage between IGN terminal on regulator and alternator B– termi-
nal. Does 28 V battery voltage exist?
Yes No
 

With key off, engine off: Remove alternator-to-regulator harness from regulator. Test for battery voltage across
sockets D and C in harness plug. Does 28 V battery voltage exist?
Alternator is defective.

Alternator is
defective.

Alternator is defective.

Regulator is defective.
Yes
Install a jumper wire from socket B in alternator-to-regulator harness plug to B+ terminal on
alternator. Momentarily (1 sec.) jumper socket A to B– terminal on alternator. 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
 
Regulator responded to overvoltage condition. Go
to Chart 3 on page 8 to troubleshoot OVCO.
Repair vehicle battery circuit wiring as necessary. Continue test.
CONNECTIONS
A F–
B F+/D+
C B–
D B+
E Phase