C.E. Niehoff & Co. N1245/N1248-3 Troubleshooting Guides - Manual (Page 5)

Page 5 TG44D
Section C: Advanced Troubleshooting
Chart 1 – No Alternator Output – N3043 Regulator
With key on, engine off: Momentarily (1 sec.) jumper D+ terminal on regulator to B+ terminal on alternator.
Touch shaft with steel tool to detect significant magnetism. Is shaft magnetized?
Yes No
Figure 6 – Alternator-to-Regulator Harness Plug

Set DMM to diode test. Connect black lead of DMM to pin B in harness
plug. Connect red lead to B-terminal or alternator. DMM should read
voltage drop. Reverse leads. DMM should read OL.
With key off, engine off: Unplug alternator-to-regulator harness.
Connect DMM across pin D and pin C in harness plug. Does battery
voltage exist?
Yes No
Alternator is defective.

Yes No

Alternator is defective.


With key on, engine off: Install a jumper from B+ terminal on alternator to pin B in harness plug. Momentarily
(1 sec.) jumper pin A to B– terminal on alternator. Touch shaft with steel tool to detect significant magnetism.
Is shaft magnetized?
Yes No
Alternator is defective.

Remove jumper from D+ to B+.
 

CONNECTIONS
A F–
B F+/D+
C B–
D B+
E Phase
When performing the following test, ensure that
the probes do not touch other pins, as an arc may
damage the pins and wiring in the harness.
CAUTION
When performing the following test, ensure that the jumpers do not touch other pins, as an arc may
damage the pins and wiring in the harness. Always connect jumper wires away from pins or not at pins.
Spark may erode pin.
CAUTION
Regulator is defective.

CAUTION
When performing the following test, do not allow jumper to contact B+ terminal more than a few
seconds. Internal fuse may blow. Wait 20 minutes before repeating test to allow fuse to reset.