Instrument Panel, Gauges and Warning Indicators: Description and Operation

GAUGES AND INDICATORS

How the Circuit Works
The indicator lights come on under various conditions in their related systems. Refer to each related system to see the entire indicator light circuit.

Coolant Temperature Gauge
Voltage applied to the coils inside the coolant temperature gauge, through fuse 9 (in the driver's under-dash fuse/relay box), generates a magnetic field. The magnetic field, controlled by the PCM, causes the gauge needle to move toward the coil with the strongest magnetic field.

Fuel Gauge and Low Fuel Indicator Light

WARNING: Do not smoke while working on the fuel system.Keep open flame away from the work area.Drain fuel only into an approved container.

The main circuit inside the gauge assembly monitors the resistance readings from the fuel gauge sending unit. Depending on the resistance value, the main circuit supplies a voltage to the coils inside the fuel gauge. The magnetic field causes the gauge needle to move. As the resistance in the sending unit varies, current through the gauge coils changes, moving the gauge needle toward the coil with the strongest magnetic field.

The fuel gauge sending unit's resistance varies from about 3 - 5 ohms at full to about 106 ohms at empty. When you turn the ignition switch to LOCK (0), the gauge remains at the last reading until you turn the ignition switch to ON (II) or START (III) again.

Voltage is supplied to the low fuel indicator light through fuse 9 (in the driver's under-dash fuse/relay box). If the main circuit inside the gauge assembly senses that the resistance in the fuel gauge sending unit is too high (when the fuel level inside the fuel tank is too low) it will provide ground to the bulb, which turns on the low fuel indicator light.

Speedometer and Odometer
The odometer and speedometer drive circuit (part of the main circuit) receive pulses from the PCM. The pulse rate increases as the car accelerates. The frequency and duration of these input pulses are measured and displayed by the speedometer, odometer, and trip meter.

Tachometer
The tachometer drive circuit (part of the main circuit) receives pulses from the PCM. The solid-state tachometer then displays these pulses as engine speed. For each 200 pulses per minute from the PCM the tachometer displays 100 RPM.