C.E. Niehoff & Co. N1609 Troubleshooting Guides User Manual
Page 5
Page 5
TG50E
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 1 – No Alternator Output – Test Charging Circuit
With DMM, check resistance across field coil. Connect red lead of DMM to socket C in alternator-to-regulator har-
ness plug. Connect black lead to socket F 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 A of alternator-to-regulator
harness plug and black lead to socket B of plug. Meter should show volt-
age drop value.
Then reverse meter lead connections. Meter should show OL
(blocking).
No
Shut down vehicle and restart engine or wait until system voltage drops below setpoint.
Does alternator function normally after restart?
Yes
No
Figure 3 – 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 A 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 F in alternator-to-regulator harness plug to B+ terminal on
alternator. Momentarily (1 sec.) jumper socket C 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 2 on page 5 to troubleshoot OVCO.
Repair vehicle battery circuit wiring as necessary. Continue test.
SOCKET CONNECTIONS
A B–
B AC
C F–
D B+
E Alt Temp Sense
F F+
G Not used