Engine Dc Control System; Introduction; Operational Analysis - Guardian 4270 Diagnostic Repair Manual

Section 5

ENGINE DC CONTROL SYSTEM

Page 18

INTRODUCTION

The engine DC control system includes all compo-
nents necessary for the operation of the engine.
Operation includes off, preheat, cranking/starting,
running, shutdown, and fault shutdown. The system
is shown schematically.

OPERATIONAL ANALYSIS

CIRCUIT CONDITION- OFF:
Battery voltage is available to the engine controller
circuit board from the unit BATTERY and via (a) the
RED battery cable, Wire 13, a 14 amp FUSE (F1),
Wire 15 and engine controller Terminal 1. However,
circuit board action is holding the circuit open and no
action can occur.
Battery voltage is available to the contacts of a
STARTER CONTACTOR (SC), but the contacts are
open.
Battery voltage is available to the contacts of a PRE-
HEAT CONTACTOR (PHC), but the contacts are
open.
Battery voltage is available to the PREHEAT
SWITCH (SW).
The switch is open and the circuit is incomplete.
Battery voltage is also available to the remote con-
nection for a remote preheat switch.
Battery voltage is available to the BATTERY
CHARGE RECTIFIER (BCR). This is used as a
return path for Battery Charge Winding current.