C.E. Niehoff & Co. N1224 Standard Troubleshooting Guides - Manual (Page 7)

Page 7
TG0045A
Section 5: Advanced Troubleshooting
(CONT’D)
Yes No
Alternator is defective.
Unplug alternator-to-regulator harness from regulator. Connect red lead from DMM to pin A in plug. Con-
nect black lead to pin C in plug. Does resistance read 1.5 ± 0.2 ohms?
Chart 3 – 28 V LED Steady RED– No Alternator Output – Test OVCO Circuit
Yes No
Reconnect cables. Replace existing regulator with known
good regulator. Run engine. Does OVCO trip?
Alternator is defective. Original regulator is defective.
T
T
T T
Yes No
Original regulator is defective.
Replace regulator with known good regulator. Run engine. Does OVCO trip?
Chart 4 – 14 V LED Steady RED– No Alternator Output – Test OVCO Circuit
Alternator is defective.
T T
Remove 28 V and 14 V positive battery cables AT BATTERY PACK before proceeding.
Yes No
Go to Chart 3.
Run engine. Is 28 V LED on regulator flashing GREEN?
T T
Yes No
With engine off, is battery voltage present at alternator 14 V B+ terminal?
Chart 2 – 14 V LED Flashing AMBER – No 14 V Alternator Output – Test Circuit
Yes No
Connect DMM red lead to pin E on alternator-to-regulator harness plug.
Connect black lead to pin C on same plug. Does battery voltage exist?
Alternator is defective.
Repair vehicle wiring
as necessary. Continue test.
T
T
Substitute a known good regulator. Run engine. Is regulator setpoint voltage present and is 14 V LED flashing GREEN?
Yes No
Original regulator was defective.
T
T
Yes No
Go to Chart 1.
Run engine. Is 28 V LED on regulator flashing GREEN?
T
T
T
T
Alternator is defective.
T