C.E. Niehoff & Co. C672 Troubleshooting Guides - Manual (Page 5)

Page 5 TG73A
Section C: On-Vehicle Troubleshooting
(CONT’D)
No Alternator Output – Test Charging Circuit
• TEST MEASUREMENTS ARE TAKEN ON HARNESS PLUG AT ALTERNATOR. TEST MEASUREMENT AT AN
EXTENDED HARNESS PLUG MAY AFFECT RESULTS.
• REMOTE-MOUNTED REGULATORS: CHECK CONDITION OF FUSES IN WIRING HARNESS BEFORE TROUBLE-
SHOOTING.
• BEFORE STARTING DIAGNOSTIC SEQUENCE, VERIFY THE FOLLOWING AND REPAIR/REPLACE IF NOT
TO SPEC:
—BATTERIES FOR STATE-OF-CHARGE (24.5-25.5 V), CONDITION, AND SECURE CONNECTIONS
—MASTER BATTERY SWITCH FOR FUNCTION
MASTER BATTERY SWITCH ON, KEY ON, ENGINE ON: Test for battery voltage at B+ terminal on alternator
to ground, then at ENG circuit on regulator to ground. Does battery voltage exist at both locations?
Yes No
Figure 5 – CEN 6-pin A10-114 Inline Harness Tool
Socket Connections
SOCKET CONNECTIONS
Socket A F –
Socket B Phase
Socket C B –
Socket D B+
Socket E D+
Socket F F+
MASTER BATTERY SWITCH ON, KEY OFF, ENGINE OFF: Readings of all five tests must pass.
1. Battery voltage test: Connect DMM red lead to socket D in test tool. Connect DMM black lead to socket C in test
tool. Battery voltage should exist.
2. Field coil resistance test: Set DMM to ohms test. Field resistance between sockets F and A in test tool should
measure nominal 1.0-1.5 ± 0.2 ohms. Field coil is defective if reading is less than 0.5 ohms or greater than 3 ohms.
3. Significant magnetism test:
a. Securely connect one jumper wire between socket F in test tool and B+ terminal on alternator.
b. Insert one end of second jumper wire in socket A in test tool. Momentarily (1 sec.) touch other end of second
jumper wire to alternator B– terminal. Spark will occur at B– terminal. Touch steel tool to shaft to detect
significant magnetism.
c. Remove both jumper wires.
4. Turn off master battery switch. Disconnect B+ battery cable on alternator. Set DMM to diode test. Connect black
lead on DMM to socket E in test tool and red lead to B+ terminal on alternator. DMM should read OL. Reverse
leads. DMM should read OL again. Reconnect B+ battery cable to alternator. Turn on master battery switch.
5. Phase supply test: Set DMM to diode test. Connect DMM black lead to socket B in test tool. Connect red lead to
alternator B+ terminal. DMM should read blocking in this direction. Then reverse leads. DMM should read flow
in this direction. Repeat for socket B and B– terminal. Tests should read flow in one direction and blocking in
the other direction.
Yes No
Alternator is defective.
ENGINE OFF: Disconnect 6-pin alternator-to-
regulator harness plug at regulator and connect
CEN A10-114 inline test tool to harness plug end
only. Make sure connections are secure.
Regulator is defective.
Repair vehicle wiring as necessary. Run engine
and re-test charging circuit. Is charging system
performing properly?
System is operative.
No Yes
A B C D E F
If you have questions about your alternator or any of these instructions, or if you need to locate a Factory Authorized Service Dealer, please contact us at:
C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA
TEL: 800.643.4633 USA and Canada • TEL: 847.866.6030 outside USA and Canada • FAX: 847.492.1242
E-mail us at [email protected]
Figure 6 – A2-342 3-pin Harness
Pin Connections
PIN CONNECTIONS
Pin A D+
Pin B Phase out
Pin C Eng