MOTOR TRUCK SERVICE MANUAL
INSTRUMENTS
DESCRIPTION
In addition, some instruments are vapor pressure or
pressure expansion type. The vapor pressure
Standard instruments on a vehicle include an
instrument operates from heating ether type liquid in an
ammeter or charge indicator, fuel gauge, oil pressure
immersion bulb, causing the gauge to change the
gauge, temperature gauge and speedometer. Other
location of the pointer. Pressure expansion type gauges
gauges such as air, vacuum and tachometer may be
operate by direct pressure through a line which connects
included on vehicles of various types. However, all
to the gauge.
these gauges or receivers come under the classification
of instruments.
Fig. 3 illustrates a typical wiring diagram with an
external mounted constant voltage regulator.
Electrical instrument gauges as well as the panel
lights of the cluster are connected to the vehicle
electrical system either by individual wires or printed
circuit boards, Fig. 1.
Fig. 1. Electrical Instrument Gauge Printed Circuit
Board.
The printed circuit board consists of a composition
board on which metallic strips are placed through a
photographic process. The board is then covered with
an insulating material except where contact with
Fig. 2. Internal View of Receivers with and without
Voltage Regulator. View of External Mounted Regulator.
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