1989-Montero · meters gauges · страница 3 из 16 · Открыть оригинал PDF ↗
Диагностика и устранение неисправностей
METER CIRCUIT
OPERATION
Fuel Gauge
When the ignition switch is turned to “ON”,
current flows through fuse No. 3 fuel gauge,
fuel gauge unit and ground, in turn operating
the fuel gauge.
When fuel level is high, the fuel gauge unit
internal resistance is small so that the current
passing through the circuit is relatively large.
This causes the gauge pointer to swing to-
wards “F”.
When fuel level becomes low, the unit internal
resistance is increased, so only a small current
flows the circuit and the gauge pointer swings
towards “E”.
Inside the fuel gauge, there is a voltage limiter
which functions to maintain a constant output
voltage (at 7V) to the gauge units (fuel gauge
unit and engine coolant temperature gauge
unit).
Engine Coolant Temperature Gauge
When the ignition switch is turned to “ON”,
current flows through fuse No. 3, engine
coolant temperature gauge, engine coolant
temperature gauge unit, and ground, in turn,
operating the engine coolant temperature
gauge.
When coolant temperature is high, the gauge
unit internal resistance is small so that the
current passing through the circuit is relatively
large. This causes the gauge pointer to swing
towards “H”.
Oil-pressure gauge
With the ignition key at the “ON” position,
current flows to fuse No. 3, oil-pressure
gauge, the Oil-pressure gauge unit, and
ground, and the oil-pressure gauge is acti-
vated.
When the oil pressure is high, the contacts
(within the unit) close for a long time, with the
result that the amount of current flowing
through the circuit is great, and the gauge’s
indicator indicates at the high-pressure area.
With the oil pressure is low, the contacts
(within the unit) open for a short time, with
the result that the amount of current flowing
through the circuit is low, and the gauge’s
indicator indicates at the low-pressure area.
Brake Warning Light
l When the ignition switch is turned to “ON”
and before the engine starts, current flows
through fuse No. 3, brake warning light, alter-
nator and ground. The brake warning light
goes on and stays on until the engine starts.
The light goes off once the engine starts.
Burnt-out bulb check.
l If the brake fluid level falls below the preset
level or the parking brake is applied, the brake
fluid level sensor switch or the parking brake
switch contacts close. This causes current to
flow through the brake warning light and brake
fluid level sensor or parking brake switch to
ground, causing the warning light to go on.
When coolant temperature is low, the unit
internal resistance is increased so a small
current flows in the circuit, and the gauge
pointer swings towards “C”.
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