Gauges

CIRCUIT OPERATION

Door Open Indicator
Battery voltage is applied at all times through the DOME Fuse, Junction Block 1, Audio Alarm Module, and Junction Block 3 to the Door Open Indicator in the Instrument Cluster. If any door is opened, a ground is provided for the indicator through the Audio Alarm Module and Junction Block 1 to a switch located in the door jamb. Since both power and ground are supplied to the indicator whenever a door is opened, the Door Open Indicator lights.

Oil Pressure Indicator
With the ignition switch in the "ON" or "START" position, ignition voltage is applied through the GAUGE Fuse, Audio Alarm Module, and Junction Block 3 to the Oil Pressure Indicator in the Instrument Cluster. The Oil Pressure Switch provides the ground to the indicator when there is little or no oil pressure. When the engine is not running, the Oil Pressure Switch is closed, due to the lack of oil pressure, and the indicator lights. When the engine is started, oil pressure builds up within the cylinder block and the Oil Pressure Switch opens. When this switch opens, the Oil Pressure Indicator goes out. If the oil pressure should fall below 20 kPa (3 psi) with the engine running, the Oil Pressure Indicator will light and remain lit until the oil pressure exceeds 20 kPa (3 psi).

Engine Coolant Temperature (ECT) Gauge
The pointer of the ECT Gauge is moved by the magnetic fields of two coils. The coils are at right angles to each other. Voltage is applied to coil H from the GAUGE Fuse through the Audio Alarm Module and Junction Block 3 when the ignition switch is in the "ON" or "START" position. The circuit divides at the opposite (ground) side of the coil. One path seeks a ground through coil C and the other path seeks a ground through the variable resistor in the ECT Sending Unit.

When ECT is low, resistance in the ECT Sending Unit is high. Since current will always seek the path of least resistance, current will flow through the H coil and the C coil to ground at G106. Since the length of the C coil winding is twice the length of the H coil winding, the magnetic field generated by coil C is twice as strong as the magnetic field generated by coil H. Therefore, the pointer will be pulled to the "C" position.

As ECT increases, resistance in the ECT Sending Unit decreases. Since current will always seek the path of least resistance, more current will begin to bypass the C coil and travel directly to ground through the ECT Sending Unit. Under these conditions, the coil H magnetic field becomes stronger than the coil C magnetic field and the pointer moves toward the "H" position.

Fuel Gauge
The pointer of the Fuel Gauge is moved by the magnetic fields of two coils. The coils are at right angles to each other. Voltage is applied to coil F from the GAUGE Fuse through the Audio Alarm Module and Junction Block 3 when the ignition switch is in the "ON" or "START" position. The circuit divides at the opposite (ground) side of the coil. One path seeks a ground through coil E and the other path seeks a ground through the variable resistor in the Fuel Gauge Sending Unit.

When fuel level is low, resistance in the Fuel Gauge Sending Unit is high. Since current will always seek the path of least resistance, current will flow through the F coil and the E coil to ground at G202. Since the length of the E coil winding is twice the length of the F coil winding, the magnetic field generated by coil E is twice as strong as the magnetic field generated by coil F. Therefore, the pointer will be pulled to the "E" position.

As fuel level rises, resistance in the Fuel Gauge Sending Unit decreases. Since current will always seek the path of least resistance, more current will begin to bypass the E coil and travel directly to ground through the Fuel Gauge Sending Unit. Under these conditions, the coil F magnetic field becomes stronger than the coil E magnetic field and the pointer moves toward the "F" position.

Speedometer
The Vehicle Speed Sensor (VSS) receives ignition voltage whenever the ignition switch is in the "ON" or "START" positions through the Audio Alarm Module and Junction Block 3. The VSS is permanently grounded through the Instrument Cluster to G202. When the drive wheels are rotating with the transaxle in gear, the VSS sends a square wave frequency signal to the Speedometer at the rate of approximately 2,000 pulses per mile. The Speedometer converts the frequency into a vehicle speed that is displayed on the Speedometer. The higher the frequency, the higher the vehicle speed, and the lower the frequency, the lower the vehicle speed.

Tachometer
Voltage to the Tachometer is provided from the GAUGE Fuse through the Audio Alarm Module and Junction Block 3. The Tachometer displays engine speed in rpm. Ground pulses are taken from the ignition system and sent to the Tachometer. The Tachometer responds to the frequency of the ground pulses, which increase with engine speed.