C.E. Niehoff & Co. C703/C703A & C706 Troubleshooting Guides User Manual

Page 2

Page 2

TG31K

Section A: Description/Operation

CEN C703/C703A and C706 Alternators/Regulators Description and Operation

C703/C703A 28 V (350 A) and C706 28 V (300 A) alternators are internally rectified. All windings and current-

transmitting components are non-moving, so there are no brushes or slip rings to wear out.
These alternators are externally energized when the battery master switch on the vehicle is turned on and provides

power to the regulators through the IGN circuit (the A2-341 regulator can also operate without vehicle connection to

IGN, and instead provide power by sensing rotation through the regulator’s AC circuit).
Field coil is then energized. AC is rectified into DC output through diodes in drive end rectifier housing and supplied

to the battery from the alternator B+ terminal. See schematic diagram on page 4. Alternator output current is self-
limiting and will not exceed rated capacity of alternator. Regulator maintains alternator output voltage at pre-determined
regulated setting (see Table 1 or 2 below for setpoints) as vehicle electrical loads are switched on and off.
Battery type selection and battery maintenance/function are the sole responsibilities of the customer.

A2-214 and A2-325 regulators furnished with some units include:

• External IGN terminal for energize connection.

• P terminal that can provide optional AC voltage tap. P terminal signal frequency (Hz) x 10 = alternator shaft rpm.

• D+ terminal that can provide DC voltage signal to vehicle electrical system, confirming alternator operation.

• Overvoltage cutout (OVCO) function. See page 5.

• (A2-214 only) Green-lensed LED. See page 5.

• (A2-325 only) Tricolored LED. See page 5.

• Regulator fixed (flat temperature compensation) setpoints shown in Table 1 are selected based on battery type.

Figure 2—Voltage Setpoints

Table 1 — A2-214 & A2-325 Regulator Setpoint Switch Position

Voltage Setpoints (±0.2 V)

Battery Type

Position 1

27.5 V

Maintenance

Position 2

28.0 V

Maintenance

Position 3

28.5 V

Maintenance-free

Position 4

29.0 V

Maintenance-free

Note on Group 31 batteries: If boiling or excessive gassing occurs with high voltage

setpoint (position 3), change to medium voltage setpoint (position 2).

A2-341 regulator furnished with some units includes:

• External IGN terminal that can provide optional external energize connection. This regulator can function with or

without vehicle ignition. When necessary, regulator IGN terminal can be connected to vehicle ignition source to provide
battery voltage when engine is running. Circuit should be off (no voltage present) when vehicle ignition is off or engine
is not running.

• P terminal that can provide optional AC voltage tap. P terminal signal frequency (Hz) x 10 = alternator shaft rpm.

• D+ terminal that can provide DC voltage signal to vehicle electrical system, confirming alternator operation.

• Overvoltage cutout (OVCO). See page 6.

• Tricolored LED. See page 6.

• Temperature-voltage sense/J1939 harness connector that can be used with optional harness.

— When optional temperature-voltage sense/J1939 harness is not connected, regulator will operate in fixed voltage

setting determined by the select switch position on the bottom of the regulator. See Column 2 in Table 2.

— When optional temperature-voltage sense/J1939 harness is connected, regulator will automatically optimize the

charge voltage for battery type based on temperature. Also, vehicle manufacturer-requested functions of J1939

interface are available through connector. See Column 3 in Table 2.

Figure 3—Voltage/Battery Switch

Table 2 — A2-341 Regulator Voltage/Battery Switch Position

Switch Position

T-VS/J1939 Harness Not

Connected (Voltage Select)

T-VS/J1939 Harness Connected

(Battery Select)