Guardian Technologies 4270 - Manual (Page 25)

Section 5
ENGINE DC CONTROL SYSTEM
Page 23
CIRCUIT CONDITION- FAULT SHUTDOWNS:
The engine has mounted to it a HIGH WATER TEM-
PERATURE SWITCH (HWT) and a LOW OIL PRES-
SURE SWITCH (LOS). While running, ENGINE
CONTROL circuit board action keeps Terminal 12
Wire 85 energized with battery voltage. Connected in
parallel to (Wire 85) are the LOW OIL PRESSURE
SWITCH (LOS) and HIGH WATER TEMP SWITCH
(HWT). The (LOS) has normally closed contacts.
After start-up, engine oil pressure will open the con-
tacts. The HWT has normally open contacts. High
coolant temperature will close the contacts.
Should engine water temperature exceed a preset
value, the switch contacts will close. Wire 85 from the
circuit board will connect to ground. Circuit board
action will then initiate a shutdown.
Should engine oil pressure drop below a safe pre-set
value, the switch contacts will close.
On contact closure, Wire 85 will be connected to
ground and circuit board action will initiate an engine
shutdown.
The circuit board has a time delay built into it for the
Wire 85 fault shutdowns. At STARTUP ONLY the cir-
cuit board will wait approximately six (6) seconds
before looking at the Wire 85 fault shutdowns. Once
running after the six (6) second time delay, grounding
Wire 85 through either switch will cause an immedi-
ate shutdown.
The ENGINE CONTROL circuit board also has over-
speed protection. The circuit board senses the AC
output from the stators POWER winding at Terminals
5 & 6 via Wires 22 & 44. This AC voltage and fre-
quency signal is used indirectly to monitor engine
RPM. If the frequency should increase above a pre-
set "adjustable" limit, the ENGINE CONTROL circuit
board will cause an immediate shutdown.