C.E. Niehoff & Co. C709/C725 Troubleshooting Guides - Manual (Page 4)

Page 4
TG64B
Section C: Advanced Troubleshooting
A2-329 Regulator
DESCRIPTION AND OPERATION
A2-329 Regulator with OVCO is attached directly to the
outside of alternator. Regulator setpoint has flat temper-
ature compensation. Voltage setpoint is 28.0 ±1.0 V and
14.0 ±0.5.
OVCO (overvoltage cutout) will trip at any of the
following conditions:
• 14 V side trips at voltage
higher than regulator
setpoint that exists longer than 3 seconds of reading
voltage above 16 V. OVCO feature detects overvoltage
and reacts by disabling the alternator field circuit.
This turns off alternator. OVCO circuit will reset by
either:
— Restarting engine (regulator regains control of
alternator output voltage) OR
— System voltage on both 14 and 28 volt batteries
falling below 11 V. OVCO will automatically reset.
• 28 V side trips at voltage higher than regulator
setpoint that exists longer than 3 seconds of reading
voltage above 32 V. OVCO feature detects overvoltage
and reacts by disabling the alternator field circuit.
This turns off alternator. OVCO circuit will reset by
either:
— Restarting engine (regulator regains control of
alternator output voltage) OR
— System voltage on both 14 and 28 volt batteries
falling below 11 V.
Troubleshooting
Shut down vehicle and restart engine. If alternator
functions normally after restart, a “no output condition”
was normal response of voltage regulator to overvoltage
condition. Inspect condition of electrical system, includ-
ing loose battery cables, both positive and negative. If
battery disconnects from system, it could cause overvolt-
age condition in electrical system, causing OVCO circuit
to trip.
If you have reset alternator once, and electrical system
returns to normal charge voltage condition, there may
have been a one time, overvoltage spike that caused
OVCO circuit to trip.
If OVCO circuit repeats cutout a second time in short
succession and shuts off alternator field circuit, try third
restart. If OVCO circuit repeats cutout a third time, go to
Chart 3a or 3b, page 7.