R
Page 6
TG69B
Chart 2: Test OVCO Circuit
Yes
No
1. Unplug alternator-to-regulator harness from regulator.
2. Connect DMM red lead to harness pin F.
3. Connect DMM black lead to alternator B+ terminal. Does resistance read OL?
Alternator is faulty
Replace existing regulator with known good regulator. Run engine. Does OVCO trip?
Yes
No
Alternator is faulty
Original regulator is faulty
Yes
No
1. Connect DMM red lead to harness pin A.
2. Connect DMM black lead to alternator B+ terminal. Does resistance read OL?
Alternator is faulty
Chart 3: Test Power Limiting Circuit
Section C: Advanced Troubleshooting
(CONT'D)
If you have questions about your alternator or any of these test procedures, 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]
C. E. Niehoff & Co. • 2021 Lee Street • Evanston, IL 60202 Tech Services Hotline 800-643-4633
Yes
No
1. Unplug alternator-to-regulator harness from regulator.
2. Connect DMM red lead to harness pin G.
3. Connect DMM black lead to alternator B+ terminal. Does resistance read <1 ohm?
Alternator is faulty
Replace existing regulator with known good regulator. Run engine at >4000 RPM
and add electrical load (>250 amps). Does alternator limit output as expected?
Yes
No
Power limiting circuit is operational
Original regulator is faulty
Yes
No
1. Connect DMM red lead to harness pin E.
2. Connect DMM black lead to alternator B- terminal. Does resistance read 60k-130k ohms at
room temperature?
Alternator is faulty
