C.E. Niehoff & Co. C717 Troubleshooting Guides User Manual

Page 5

Page 5

TG78A

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 IGN terminal on regulator to ground (A2-351 regulator: See page 2 for more information).

Does battery voltage exist at both locations?

Yes

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

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.

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]