Description & Operation

The instrument panel contains an electronic speedometer, tachometer (if equipped), fuel gauge, coolant temperature gauge, gear position indicator and warning light displays. Cross-coil type gauges, in which 2 intersecting coils are wound around a permanent magnet, are used.

Speedometer and odometer drive circuits receive pulses from Vehicle Speed Sensor (VSS). VSS pulse rate increases as vehicle speed increases. Tachometer drive circuit receives pulses from Engine Control Module (ECM) or Powertrain Control Module (PCM). For each 200 pulses per minute from the ECM/PCM, the tachometer displays 100 RPM.

Engine coolant temperature sending unit varies resistance from about 137 ohms at low engine temperature to 30-46 ohms at high temperature (radiator fan running). Fuel gauge sending unit varies resistance from 3-5 ohms when fuel tank is full to about 110 ohms when fuel tank is empty. When ignition switch is turned off, fuel gauge will remain at last reading until ignition switch is turned on again.

Low fuel tank indicator light circuit uses thermistor located in fuel tank unit. When the thermistor is cool, its resistance is very high. When thermistor resistance is high, not enough current can flow through low fuel indicator light circuit to illuminate indicator light. When thermistor's temperature increases, its resistance decreases allowing enough current to flow through low fuel indicator light circuit to illuminate low fuel indicator light. Fuel in fuel tank transfers heat away from thermistor fast enough to keep it cool, so thermistor's resistance stays high and low fuel indicator light does not come on. When fuel level drops below the thermistor, thermistor's temperature increases and resistance decreases. Low fuel indicator light will illuminate.