Chrysler RAM TRUCK 2500 1994 Service Manual page 399

8E - 2 INSTRUMENT PANEL AND GAUGES •
The low line cluster also includes warning lamps
for:
• low oil pressure warning
• four-wheel drive indicator
• malfunction indicator (Check Engine)
• airbag warning
• seat belt reminder
• maintenance required (emissions maintenance -
HDC 5.9L V8 & 8.0L VIO)
• upshift indicator
• brake indicator
• anti-lock brake system indicator
• turn signal indicators
• high beam indicator
The high line cluster has all the gauges of the low
line cluster and includes a 0-6000 rpm tachometer
(Fig. 2)
The high line cluster also includes warning lamps
for:
• low fuel warning
• low washer fluid indicator
GAUGES
A l l the gauges are the electro-magnetic type. When
the ignition switch is i n the OFF position each gauge
will show a reading, except the speedometer and ta­
chometer. The readings are only accurate when the
ignition switch is i n the ON position.
VOLTMETER
The voltmeter measures battery or generator out­
put voltage, whichever is greater.
OIL PRESSURE GAUGE
The oil pressure gauge pointer position is con­
trolled by a magnetic field created by electrical cur­
rent flow through the coils within the gauge. A
change i n current flow will change the magnetic field
which changes the pointer position. The oil pressure
sender is a variable resistor that changes electrical
resistance with a change i n oil pressure (calibration
values shown i n Specifications chart).
In the oil pressure indicating system, changes i n
sending unit resistance are actuated by a diaphragm
that moves as the oil pressure increases or decreases.
Low oil pressure causes high resistance. High pres­
sure causes low resistance.
COOLANT TEMPERATURE GAUGE
The coolant temperature gauge pointer position is
controlled by a magnetic field. This field is created by
electrical current flowing through the coils within the
gauge. A change in current flow will change the mag­
netic field which changes the pointer position. The
coolant temperature sending unit is a thermistor that
changes electrical resistance with a change i n coolant
temperature. As the resistance changes, the current
changes and the pointer moves to a new position (cal­
ibration values shown i n Specifications chart).
When the engine coolant is cold, the resistance of
the sending unit is high. When the engine coolant is
hot, the resistance of the sending unit is low.
FUEL GAUGE
The fuel gauge pointer position is controlled by a
magnetic field created by electrical current flow
through the coils within the gauge. A change i n cur-
Fig. 2 High Line Cluster—Typical