Base
The operation of an Indicator is explained in the operation of its circuit. See the circuit referred to for complete operation of an Indicator and the other components that work with it Only the Gages and Indicators that do not appear in other schematics are described in this section.FUEL GAGE DISPLAY
The Pointer of the Fuel Gage is moved by the magnetic fields of 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. Another goes to ground through the variable resistor of the Fuel Gage Sender.
When the tank is low, the resistance of the Sender is low. A large flow of current passes through the E coil and the Fuel Gage Sender resistor. This pulls the pointer towards E On the scale. When the tank is full, the Sender resistance is high. More current now flows through the F coil, moving the pointer to 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 INDICATOR
The Oil Pressure Indicator comes on to warn the driver when the engine oil pressure is low. Battery voltage is applied to one side of the bulb. A ground path is provided by the Oil Pressure Switch. It closes when the oil pressure is below 27 kpa (4psi) and the Indicator bulb lights. After the engine starts and normal oil pressure builds up, the Oil Pressure Switch opens. The Oil Pressure Indicator goes Out.
COOLANT TEMPERATURE INDICATOR
The Coolant Temperature Indicator warns the driver of a high coolant temperature. With the ignition Switch in RUN, BULB TEST or START. voltage from Fuse 11 is applied to the Coolant Temperature Indicator. The bulb is grounded through the Coolant Temperature Switch. The switch closes when the coolant temperature exceeds 258°F (126°C). The bulb lights.
SPEEDOMETER AND ODOMETER
The Vehicle Speed Sensor (VSS) generates a signal that is processed by the Solid State ECM to supply inputs to the Cruise Control Module, the Speedometer and the Odometer.
The Vehicle Speed Sensor is mounted in the transaxle. A magnet rotates near a coil, producing voltage pulses in the coil. The frequency of the AC voltage coming from this coil is directly proportional to the vehicle speed.
The ECM takes the voltage pulses from the sensor and uses them to close a Solid State output switch. The output terminal is switched to ground at a rate that is proportional to the speed of the car. The Speedometer and Odometer are switched at 4000 pulses per mile.
The Speedometer and the Odometer are operated by a circuit board in the cluster. This circuit board converts the pulses received from the ECM into a control signal for the Vacuum Fluorescent Displays.
SERVICE ENGINE SOON INDICATOR
The SERVICE ENGINE SOON indicator serves as a warning light to tell the driver that a problem has occurred and the car should be serviced. It is also used by the technician to read out diagnostic codes to help diagnose system problems.
The indicator receives battery voltage in RUN, BULB TEST and START. The ECM provides a switched path to ground.
LOW COOLANT INDICATOR
The LOW COOLANT Indicator comes on to warn the driver when a low level of coolant exists in the radiator. Battery voltage is applied in RUN, BULB TEST and START. The ECM provides a switched path to ground when the voltage output from the Coolant Level and Corrosivity Sensor is at or above 4.0 volts.