Page 2
TG0017B
Section 1: Wiring Diagram
CEN N1505-1, N1237-1, and N1225-1
Dual Voltage Alternators Description
and Operation
N1505-1
28 V 100 A and
N1237-1/N1225-1
28 V
200 A alternators all with optional 28 V/14 V (50 A
maximum on 14 V) are internally rectified. All wind-
ings and current-transmitting components are non-
moving, so there are no brushes or slip rings to wear
out.
After engine is running,
N3135
regulator receives
energize signal. Regulator monitors alternator rotation
and provides field current only when it detects alerna-
tor shaft rotating at suitable speed.
After regulator detects alternator rotation, it gradually
applies field current, preventing an abrupt mechani-
cal load on accessory drive system. The soft start may
take up to 10 seconds at full electrical load.
N3135
regulator used with these units also
• is negative temperature compensated. Setpoints
are 28.0 ± 0.2 V and 14.0 ± 0.2 V at 75° F.
• provides overvoltage cutout (OVCO). Regulator will
trip OVCO when system voltage rises above 32 V
in a 28 V system (16 V in a 14 V system) for longer
than 2 seconds. OVCO feature detects high volt-
age and reacts by signaling relay in F– alternator
circuit to open, turning off alternator. Restarting
engine resets OVCO circuit.
• maintains alternator output voltage at regulated
settings as vehicle electrical loads are switched
on and off.
B– terminal
Figure 2 — N1505-1/N1237-1/N1225-1 Alternators with N3135 Regulator Wiring Diagram
Figure 1 — N1505-1/N1237-1/N1225-1 Alternators and
N3135 Regulator Terminals
14 V B+
terminal
28 V B+
terminal
14 V
AC
IGN
AC terminal
IGN terminal
• can be used in single or dual voltage with these
alternators.
— Allows single-voltage operation (28 V only).
14 V is not available as a single voltage appli-
cation with this regulator.
— Provides optional 28 V/14 V output only from
the regulator when phase cable from alterna-
tor is connected to regulator.
R
Section 1: Wiring Diagram
Page 2
TG17C
