Komatsu 830E-AC Shop Manual page 219

Hot Switch Inverter (Not Used)
The optional oil level card is used to turn on the low
oil level indicator light to warn the operator that the
engine oil/hydraulic tank oil level is below acceptable
levels. The oil float is connected to a variable resis-
tor. As the oil level decreases, the resistance goes
down, causing Q3 to turn on and grounding the indi-
cator light and alarm horn.
The optional temperature card is used to turn on the
high oil temperature indicator light. The indicator light
tells the operator hydraulic tank oil temperature has
exceeded acceptable levels. Normal temperature
setting is 121°C (250°F). As the temperature goes
up, the resistance in the probe decreases providing a
ground path for the indicator light and alarm horn.
Temperature and Latch
The temperature and latch card has two circuits to
operate two different indicator lights. The tempera-
ture circuit is controlled by a coolant temperature
sensor which decreases electrical resistance as its
temperature increases. It will have a resistance of
approximately 1000 ohms at 85°C (185°F) and 500
ohms at 121°C (250°F). The normal setting is 96°C
(204°F).
When the temperature is low and the resistance is
high, Q1 is off and no high temperature indication
occurs. When the coolant temperature is excessive,
resistance decreases to a point where Q1 will turn on
and ground the flasher through D8, the alarm horn
through D12, and the high temperature light through
terminal D8. R14 can adjust the temperature (resis-
tance) at which the circuit is activated.
NOTE: Some electronic engine controls monitor
coolant temperature. If the engine controls monitor
the circuit, a 2K ohm resistor is installed to replace
the temperature sensor and disable the AID system
circuit.
The latch circuit monitors the accumulator precharge
pressure switches. When one of the pressure
switches closes, Q5, which supplies power to the
gate of SCR Q7, will be turned off. With Q7 turned
on, Q9 will supply the ground path to turn on the low
accumulator precharge indicator light and sound the
alarm horn. The indicator light is connected to 12F
and will flash off and on. The SCR will remain on until
power is removed from the card by turning the key
switch OFF.
D03036 10/06
Coolant Level & Flasher
The coolant level and flasher card contains two sepa-
rate circuits. The flasher circuit at the top of the card
has Q12 transistor biased to be saturated when no
malfunction is present, resulting in 24 volt positive
output on pin "H" of the card and on wire 12F. When
an indicating circuit is activated, the ground side of
the circuit connected to card pin "K" is grounded.
Q12 will turn off initially and then after a delay,
adjusted by R20, will turn on and off to give the inter-
mittent 24 volt output.
The other half of the circuitry on the coolant level and
flasher card operates the coolant level light. The
water level probe connected to terminal B11 grounds
the 31L circuit when the coolant in the radiator is
above the probe position. The coolant saturates the
probe and electrically grounds the circuit. When the
circuit is grounded, Q6 transistor is off, resulting in no
indication. When the coolant level drops below the
probe, 31L is no longer grounded and Q6 turns on to
ground the flasher through D5, the coolant level light
through terminal D11, and the alarm horn through
D6. The light and alarm horn will operate intermit-
tently as their 24 volt supply is from circuit 12F, the
flasher output.
NOTE: Some electronic engine controls monitor
coolant level. If the engine controls monitor the
circuit, a 2K
probe and disable the AID system circuit.
24VDC Electrical System Components
Ω
resistor is installed to replace the
D3-9