Gages

VOLTMETER

The Voltmeter measures the electrical system voltage with the Ignition Switch in RUN, BULB TEST or START. With the engine stopped, the Voltmeter indicates battery condition. With the engine running. the Voltmeter indicates Charging System operation.

TACHOMETER

The Tachometer displays engine speed in rpm. Voltage pulses are taken from the Ignition System and sent to the Tachometer. It responds to the frequency of the voltage pulses which increase with engine speed. Solid State circuits process these pulses into a signal that drives the pointer of the meter.

FUEL GAGE

The pointer of the Fuel Gage is moved by the magnetic field of the two coils. The coils are at right angles to each other. Battery voltage is applied to the E coil and the circuit divides at the opposite end of this coil. One path continues to ground through the F coil. The other path grounds through the variable resistor of the Fuel Gage Sender.

When the tank is low, the resistance of the sender is low (0 ohms). A large flow of current passes through the E coil and the Fuel Gage Sender resistor. This moves the pointer towards E on the scale. When the tank is full, the sender resistance is high (90 ohms). More current flows through the F coil, moving the pointer towards F on the scale.

With two coils operating the pointer. the gage is not affected by changes in the voltage of the system.

OIL PRESSURE GAGE

The engine oil pressure is displayed by the Oil Pressure Gage. The Pointer of the gage is moved by two coils, and its operation is similar to that of the Fuel Gage.

The Fuel Pump/Oil Pressure Switch/Sender is connected to the junction of the two coils. It has low resistance when oil pressure is low, and 90 ohms resistance when the oil pressure is high. This changing resistance changes the current flow through the coils to move the pointer from 0 to 80 PSI.

COOLANT TEMPERATURE GAGE

The Coolant Temperature Gage is operated by two coils. Battery voltage is applied to both coils. One is grounded directly and the other is grounded through the Coolant Temperature Sender. This has 55 ohms resistance at 260°F (hot coolant) and its resistance increases at lower temperatures. Resistance is approximately 1365 ohms at 100°F. This causes the current through the Sender and one coil to increase as the coolant temperature increases. This moves the pointer.

LOW FUEL INDICATOR

The low Fuel Indicator located in the Instrument Cluster is controlled by a Solid State buffer which reads the same Fuel Gage Sender input sent to the Fuel Gage. When the resistance of the Fuel Gage Sender drops below a certain point, the indicator control circuit lights the Low Fuel Indicator.

CHECK GAUGES INDICATOR

The Check Gauges Indicator is controlled by a Solid State buffer located in the Instrument Cluster. This buffer receives inputs from the Fuel Pump/Oil Pressure Sender/Switch, Coolant Temperature Sender and the Generator. When any of these components indicate that a gage is out of the normal operating range. The indicator control circuit grounds the CHECK GAUGES Indicator, causing it to light.

LOW COOLANT INDICATOR

The Low Coolant Indicator comes on to warn the driver when a low coolant level exists. Battery voltage is applied to the Indicator in RUN, BULB TEST or START. Ground is provided to the indicator through the Coolant Level Switch.