Circuit Operation

FUEL GAGE
The pointer of the Fuel Gage 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 IG-COIL Fuse. The circuit divides at the opposite (ground) side of the coil. One path seeks a ground through coil E to G 105 and the other path seeks a ground through the variable resistor in the Fuel Level Sensor.

When fuel level is low, resistance in the Fuel Level Sensor is high. Since current will always seek the path of least resistance, current will flow through coil F and coil E to ground at G105. Because the length of the E coil winding is twice the length of the F coil winding, the magnetic field generated by the E coil is twice as strong as the magnetic field generated by the F coil. Therefore, the pointer will be pulled to the "E" position.

As fuel level increases, resistance in the Fuel Level Sensor 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 Level Sensor. Under these conditions, the coil F magnetic field becomes stronger than the coil E magnetic field and the pointer moves toward the "F" position.

ENGINE COOLANT TEMPERATURE (ECT) GAGE
The pointer of the Engine Coolant Temperature (ECT) Gage 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 IG-COIL Fuse. 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 Sensor.

When ECT is low, resistance in the ECT Sensor 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 G105. Because 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 Sensor 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 Sensor. Under these conditions, the coil H magnetic field becomes stronger than the coil C magnetic field and the pointer moves toward the "H" position.

OIL PRESSURE INDICATOR
With the Ignition Switch in the "ON" or "START" position, battery voltage is applied through the IG-COIL Fuse to the Oil Pressure Indicator in the I/P Cluster Assembly. If engine oil pressure should fall below 31 kPa (4.5 psi), the Oil Pressure Switch located in the cylinder block closes. When this switch is closed, a ground path is provided to the Oil Pressure Indicator and the bulb lights.

TACHOMETER (OPTIONAL)
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. There is also a Noise Suppressor Filter in the circuit that rounds off the pulses and removes voltage spikes.