Guardian Technologies 4270 manual Circuit CONDITION- Fault Shutdowns

Section 5

ENGINE DC CONTROL SYSTEM

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.

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