Doosan L6-60HZ-T4F Operation And Maintenance Manual page 41

Maintenance
Engine Protection Shutdown System
The operation of the Engine Protection Shutdown System should be checked every month or
whenever it appears not to be operating properly. The three switches involved in this protective
shutdown system are the Engine Coolant High Temperature Switch, the Engine Oil Pressure
Switch and the Low Fuel Switch.
The Engine Oil Pressure Switch prevents the engine from operating with low oil pressure.
Once a month, remove a wire from the engine oil pressure switch (ground the wire on LSC
models only) to check the shutdown system for proper operation. Test the Engine Oil Pressure
Switch by removing it and connecting it to a source of controlled pressure while monitoring an
ohmmeter connected to the switch terminals. On the L6, L8, LS models, as pressure is applied
slowly from the controlled source, the switch should close at 12 psi (84 kPa) and show
continuity through the contacts. As pressure is slowly decreased to 10 psi (70 kPa) the
contacts should open and the ohmmeter should show a lack of continuity through the contacts.
On LSC model, as pressure is applied slowly, the switch should open at 6.5 psi (49 kPa) and
show open circuit on the contacts. As the pressure is slowly decreased, the contact should
close and the ohmmeter should show continuity through the contact. Replace a defective
switch before continuing to operate the unit.
Once a year, the Engine Coolant High Temperature Switch should be tested. Remove switch
from the unit and place it in a bath of heated oil. The Engine Coolant High Temperature Switch
will require a temperature of approximately 220°F (104°C) to actuate.
NOTE: The Engine Temperature Switch does NOT offer protection when
NO coolant is present. Test the switch operation by connecting an
ohmmeter between the two wire terminals. The ohmmeter should show
zero ohms. When the switch is placed in the heated oil bath and its
contact closed, the ohmmeter should indicate zero ohms. Tap the switch
lightly during the checking operation.
Replace any defective switch before continuing to operate the unit.
Never operate the unit with a defective safety shutdown switch or with a
by-passed or disconnected switch.
Control Compartment
Every six months or 500 hours with the unit OFF, perform visual inspection for loose
connections, dirt, arcing, or damage to electrical components.
CAUTION
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Operating & Maintenance Manual
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