Base Cluster

CIRCUIT OPERATION
See the circuit referred to for the complete operation of an indicator and other components that work with it. Only the indicators that do not appear in other schematics are described in this section.

SPEEDOMETER AND ODOMETER
The Vehicle Speed Sensor (VSS) generates a signal that indicates the speed of the solid state Powertrain Control Module (PCM) to supply inputs to the Cruise Control Module, Speedometer and 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 depends on the vehicle speed. The VSS sends pulses to the PCM at the rate of 40,000 pulses per mile.

The PCM 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 vehicle. The Speedometer and Odometer are switched at 4,000 pulses per mile.

"LOW COOLANT" INDICATOR
The "LOW COOLANT" indicator receives battery voltage with the ignition Switch in "RUN," "BULB TEST" or "START." The indicator is grounded by the Coolant Level Switch with the coolant level in the Coolant Reservoir below a minimum recommended level.

"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 Fuel Pump/Oil Pressure Switch. It closes when the oil pressure is below 26 kPa (4 psi) and the Indicator bulb lights. After the engine starts and normal oil pressure builds up, the Fuel Pump/Oil Pressure Switch opens. The "OIL PRESSURE" Indicator goes out.

"COOLANT TEMPERATURE" INDICATOR
The "COOLANT TEMPERATURE" Indicator receives battery voltage with the Ignition Switch in "RUN," "BULB TEST" or "START." The Indicator is grounded by the Coolant Temperature Switch with the coolant temperature above 260°F (127°C). This indicator is also grounded by the Ignition Switch with the Ignition Switch in "BULB TEST," or "START" as a bulb check.

FUEL GAGE
A potentiometer is built into the Fuel Sender Assembly. When the Fuel Tank is full, the resistance throughout the potentiometer is approximately 88 ohms, and at empty, the resistance is approximately 1.0 ohm. The Fuel Gage applies voltage through CKT 30 to the potentiometer. As the resistance of the potentiometer decreases, the Fuel Gage senses a smaller voltage drop across the potentiometer, indicating a lower fuel level. As the resistance of the potentiometer increases, the Fuel Gage senses larger voltage drop across the potentiometer, indicating a higher fuel level.