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Engine Temperature Sending Unit The engine temperature sending unit shown in Figure
5, and, like the fuel level tank unit operates on a principle of
varying resistance. This resistance variance is made possible by the
use of a special resistor that has a negative temperature co-efficient.
When the temperature of the coolant and the resistor are cold, the
resistance of the resistor is high. Gradually as the temperature
of the coolant and the resistor increases, the resistance decreases.
The electrical circuit for the temperature indicating system grounds
through this resistor. |
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3. FUEL LEVEL INDICATING SYSTEM Turning the ignition key on, connects the system
to the battery or charging system voltage. The function of the voltage
limiter is to regulate this input voltage from the car battery or
charging system to an average voltage of approximately 5 volts D.C. The effect of this constant voltage supply is to
cause the balance of the system to be sensitive to changes in the
value of resistance at the tank unit only. When the fuel level is low or empty, the resistance
is increased which decreases the current flow and consequently positions
the panel gauge pointer to low or empty, as shown in Figure 6. |
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When the tank is full, the float level
is at the top, the minimum resistance is in the circuit and the
flow of current in the circuit is high. The panel gauge pointer
will be moved across the dial to indicate a full tank, (See Figure
7). |
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4. THE TEMPERATURE INDICATING SYSTEM The operation of the temperature indicating system
is identical in operation with the fuel system with the exception
of the method of varying the resistance of the sending unit. In
this system the resistance varies in direct relation to the temperature
of the coolant. Any change in the coolant temperature causes a like
change in the resistor incorporated in the engine sending unit. When the engine is cold the resistance of the disc in the temperature sending unit is high and a low temperature will be indicated. (Refer to Figure 8). |
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As the engine temperature increases the resistance of the temperature sending unit disc starts to decrease. A resultant increase in the current flow will occur causing the gauge pointer to indicate the increase in engine temperature, as shown in Figure 9. |
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5. INSTRUMENT TESTING
The fuel and temperature gauges may be tested for operation
and accuracy both in the car and on the service bench. Tests of the gauges sending
units, loose connections, resistance and broken wiring may be made with the
use of electric gauge Tester C-3826. The ammeter is tested with a conventional
ammeter-voltmeter tester. Do not connect full battery voltage directly to
the gauges.
The thermal gauges operate on approximately 5 volts, and a voltage
limiter is mounted on the back of the instrument cluster on Dodge models and
in the fuel gauge on DART models to reduce the battery voltage from 12 to 5
volts. As a safety precaution the battery negative ground cable should always
be removed from the battery before any corrective work is attempted that pertains
to gauges and switches in the instrument panel.
6. TESTING GAUGES (IN VEHICLE) Voltage
Limiter
If both the temperature and the fuel gauge are not functioning
properly it is an indication that the voltage limiter is responsible.
A quick test to determine if trouble may be in the voltage limiter
is to connect a voltmeter to the temperature sending unit and a ground. Turn
on the ignition switch, a fluctuating voltmeter indicates voltage limiter is
operating and trouble is elsewhere.
Temperature Gauge
Disconnect the terminal from the temperature sending unit on
the engine. Connect one test lead of Tester C-3826 to the terminal and the other
test lead to a good ground. Place the pointer of the gauge tester on the "L"
position and turn the ignition switch to "on". The temperature gauge
should show "C" plus or minus 1/8 inch. Thermal gauges are slow
in operation. Allow time for gauge to heat up.
Place the pointer on the tester on the "M" position
and the temperature gauge should advance to the driving range of ½
position of the dial. Place the pointer of the tester in the "H" position
and the gauge should advance to the "H" position of the dial.
Should the gauge respond to the above tests, but not operate when the terminal is attached to the sending unit, indications are of a defective sending unit and it should be replaced. Should the gauge fail to respond to the above tests indications are of possible loose connections, broken wire, or defective gauge. The instrument cluster should be removed for further inspection.
Fuel Gauge
Raise car on lift. Disconnect the terminal from tank unit. Attach
one lead of the gauge tester to the disconnected terminal. Connect the other
lead of the tester to a good ground.
With the ignition switch turned on and the gauge tester in the
"L" position, the fuel gauge should show "E" or minus 3/32
inch. This tolerance permits a small reserve of fuel at the "E"
position.
With the gauge tester in the "M" position, the fuel
gauge should slowly advance to the ½ position, plus or minus 1/16 inch.
With the gauge tester in the "H" position the fuel gauge should advance
to "F" position, plus or minus 3/32 inch.
Should the gauge respond to the above tests using the C-3826
Tester, but does not respond when the wire is connected to the tank unit, the
trouble is in the tank unit. If the gauge does not respond to the tests using
C-3826 Tester indications are of possible loose connections, broken wire, or
a defective fuel gauge. The instrument cluster should be removed for further
inspection.
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Dodge 1963 63 Polara mopar Polara 383 426 318 313 330 440 dodge dodge 63 63 63 1963 1963 mopar mopar restoration restoration max wedge wedge ram ram polara 330 440 220 dart 880 technical details production New Zealand Kiwi New Zealand figures |
Copyright © 2001 Bruce Cresswell |
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