C.E. Niehoff & Co. N1128 Troubleshooting Guides - Manual (Page 5)

Page 5
TG0027A
N3212 Regulator
DESCRIPTION AND OPERATION
N3212 Regulator with OVCO is remote-mounted no
more than 12 incles from the alternator. Regulator
setpoint has negative temperature compensation. At
75ºF, the setting is 28.2 V for 28 V system and 14.1 V
for 14 V system.
Main diagnostic feature of
N3212 regulator consists
of two bicolored (amber, green) LEDs located on the
side of the regulator. One LED indicates 28 V system
performance, the other LED indicates 14 V system
performance. The two LEDs work independently of
each other. See Table 2 for diagnostic features and
LED explanations.
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 2 seconds of
reading voltage above 16 V. OVCO feature detects
overvoltage and reacts by signaling relay in F–
alternator circuit to open. This turns off alterna-
tor (14 V LED is flashing AMBER /28 V LED is
off). OVCO circuit will reset by either:
— Restarting engine (regulator regains control of
alternator output voltage and resets OVCO)
OR
— System falling below 11 V. OVCO will auto-
matically reset.
• 28 V side trips at voltage higher than regulator
setpoint that exists longer than 2 seconds of
reading voltage above 32 V. OVCO feature detects
overvoltage and reacts by signaling relay in F–
alternator circuit to open. This turns off alterna-
tor (28 V LED is flashing AMBER / 14 V LED is
off). OVCO circuit will reset by either:
— Restarting engine (regulator regains control of
alternator output voltage and resets OVCO)
OR
— System falling below 22 V. OVCO will auto-
matically reset.
TROUBLESHOOTING
Shut down vehicle and restart engine . If alternator
functions normally after restart, a “no output condi-
tion” was normal response of voltage regulator to
overvoltage condition. Inspect condition of electrical
system.
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 F– circuit, try
third restart. If OVCO circuit repeats cutout a third
time, check color of LEDs while engine is running.
28 V LED flashing AMBER / 14 V LED off—go to
Chart 4, page 8.
14 V LED flashing AMBER /28 V LED off—go to
Chart 3, page 8.
Section 4: Advanced Troubleshooting
N3212 LED COLOR N3212 STATUS
TABLE 2 – N3212 Regulator LED Diagnostics
Regulator is not energized. Measure IGN terminal voltage.
If voltage is above 21 V, regulator is defective. Off (Clear)
Respective system voltage is below regulated setting or is
processing soft start (20-second delay). Steady AMBER
Respective system voltage is reading high voltage.
Flashing AMBER
(either 28 V or 14 V)
GREEN Normal operation (respective system voltage is at regulated setting)
Alternator is shut down and is not producing power for either
voltage. 28 V side trips after 2 seconds of reading voltage
above 32 V. 14 V side trips after 2 seconds of reading voltage
above 16 V. Regulator remains in this mode until reset by
restarting engine or if system voltage drops below 22 V or 11
V, respectively. See Chart 3 on page 8 of Troubleshooting
Guide for 28V systems, Chart 4 for 14 V systems. AMBER
(either 28 V or 14 V
with the other LED
off)
GREEN
(both flashing once
every 5 sec.) Regulator is energized, but waiting for AC signal from alternator.