Figure 1.6 - Low Coolant Level Sensor
The engine control board receives AC frequency sig-
nals from an engine run winding in the alternator.
Should AC frequency exceed about 72 Hertz for three
seconds or 75 Hertz instantaneously, the engine
shuts down and the overspeed LED turns on. Should
AC frequency exceed about 72 Hertz, circuit board
action will automatically shutdown the engine (Figure
Figure 1.7 - Printed Circuit Board Assembly
RPM SENSOR LOSS
If the engine control board does not receive a proper
rpm signal from the starter during cranking or run-
ning, it shuts down the engine on rpm sensor loss
and flash the overspeed LED.
The engine control board uses a cyclic cranking
process when attempting to start the engine. The first
crank cycle is a 15-second crank followed by a seven-
second rest. This is followed by five more crank
cycles each with a seven second crank followed by a
If the engine fails to start after all six attempts, the
start attempt is stopped and the overcrank LED
Power Systems, Inc.
Section 1 — General Information
Guardian 40kW Liquid-cooled Generators
The engine control board continually monitors the
battery voltage and turns on the low battery LED if
the battery voltage falls below 11.0 VDC for one
minute. Low battery voltage is a non-latching alarm,
which will automatically clear if the battery voltage
rises above 11.0 VDC.
The control system will not attempt to start the
engine if there is a low battery condition, however, if
the engine is already running when the low battery
condition occurs, the engine will continue to run as
long as possible.
Battery voltage is NOT monitored during the crank
If the engine control board shuts down the generator
for any of the above reasons, the engine remains
stopped until the alarm is cleared by placing the
AUTO/OFF/MANUAL switch into the OFF position.
These fuses are located on the front panel of the con-
trol system. They protect the panel wiring and com-
ponents from damaging overload. Always remove the
15 amp main fuse before working on the generator.
The unit will not start or crank if this fuse is blown.
Replace the fuse with one of the same size, type, and
rating (main AGC-15, battery charger AG4).
1.8.1 UNPACKING PRECAUTIONS
Handle shipping cartons and crates with care. Use
care to avoid damage from dropping, bumping, colli-
After unpacking, carefully inspect the generator for
any damage that may have occurred during ship-
ment. If loss or damage is noted at the time of deliv-
ery, have the person(s) making delivery note all dam-
age on the freight bill or affix his signature under the
consignor's memo of loss or damage.
LIFTING THE GENERATOR
When lifting or hoisting equipment is used,
be careful not to touch overhead power lines.
The generators weight of more than 1400
pounds requires proper tools, equipment, and
qualified personnel to be used in all phases of
handling and unpacking.