Gages (UB3)

The operation of an individual indicator is described along with its circuit. Refer to the schematic and text for the circuit that is referenced below each indicator.

FUEL DISPLAY

The Fuel Gage Sender provides a signal to the Instrument Cluster that is related to the fuel level. With a full tank the Fuel Gage Sender resistance is 88 ohms. and with an empty tank the resistance is less than 18 ohms. The Instrument Cluster electronics converts the analog signal from the Fuel Gage Sender to a digital signal which controls the vacuum fluorescent Fuel

Gage Display. When 3 or fewer bars are lit the word LOW is illuminated. With only 1 bar lit, the word LOW flashes on and off.

TEMPERATURE DISPLAY

The Coolant Temperature Sender provides a signal to the Instrument Cluster that is related to the engine's temperature. With the engine at 100°F the sender resistance is 1320 ohms and only one bar is lit. When the engine reaches a temperature of 280°F all 16 bars will light. Beginning with the illumination of the thirteenth bar the word HOT will begin flashing. The Temperature Gage Display receives its signals through the Instrument Cluster, which is connected to the Coolant Temperature Sender.

OIL PRESSURE DISPLAY

The Oil Pressure Sender provides a signal to the Cluster that is related to the Oil Pressure. At 81 PSI all 16 bars are lit and the sender has a resistance of 84 ohms. At 7 PSI the first or second bars are illuminated and the word LOW turns off. The Oil Pressure Display receives its signals through the Instrument Cluster which is directly connected to the Oil Pressure Sender.

VOLTS DISPLAY

The Instrument Cluster receives battery voltage from the incoming power leads- The Instrument Cluster's internal circuitry converts the analog voltage to digital voltage where it is displayed by the Volts Gage. At 10 volts the first bar is illuminated. For every half volt above 10 volts one additional bar is illuminated until the sixteenth bar is illuminated at 17.5 volts.

TACHOMETER DISPLAY

The Tachometer is an analog display with a range from 0 to 7000 rpm. The redline is engine dependent. The display consists of 71 bars. Bars 2 thru 6 are activated simultaneously for speeds from 0 to 500 rpm. From the 7th to the 31st bar (3000 rpm), each bar is independently controlled and represents 100 rpm increments. Beyond the 31st bar the bars are tied together in pairs. Each pair represents 200 rpm.

The Tachometer data is supplied to the cluster on the Serial Data Line.

PRNDL DISPLAY

The PRNDL Display consists of 7 indicators, Park, R, N, (D), D, 2, 1. Gear selection is shown by the illumination of a rectangular box around the appropriate letter. The PRN(D)DL21 select is mechanically operated.

SPEEDOMETER and ODOMETER DISPLAYS

The Odometer and Trip Odometer are digital displays. The Trip Odometer memory is maintained with the ignition "OFF". its maximum display is 999.9 miles (1609.3 Km/h) and will automatically reset when this limit is reached. The Trip Odometer can be manually reset only with the Odometer in the "trip" mode. The Odometer maximum display is 621,503 miles (999.999 Km). The Odometer retains its memory even when the battery is disconnected.

The Speedometer consists of both an analog and a digital display. The analog display consists of 91 bars. The bars light in pairs. Each pair of bars represents 2 MPH (4Km/h). The segments above 85 MPH (138 Km/h) will not light except during the initialization sequence.

The digital display shows the vehicle speed in increments of 1 MPH (1 Km/h). The digital display will show actual vehicle speed.

The Odometers and the Speedometer receive vehicle speed information from the Vehicle Speed Sensor through the ECM and the 389 circuit.

SERVICE ENGINE SOON INDICATOR

The SERVICE ENG. SOON Indicator serves as a warning light to tell the driver that a problem has occurred and the car should be serviced. It is also used by the technician to help read out diagnostic codes to help diagnose system problems.

The Indicator receives battery voltage in RUN. BULB TEST and START. The ECM provides a switched path to ground.

LOW COOLANT INDICATOR

The LOW COOLANT Indicator comes on to warn the driver when a low level of coolant exists in the radiator. Battery voltage is applied in RUN, BULB TEST and START. The ECM provides a switched path to ground.

TRIP/SEASON SWITCH

The Trip/Season Switch is used to change between the Trip Odometer and Season Odometer display.

Depressing the Trip/Season Switch (with Season Odometer displayed) will display the Trip Odometer. Depressing the Reset Switch (after the Trip Odometer is displayed) resets the Trip Odometer to zero. Depressing the Trip/Season Switch again (with the Trip Odometer displayed) returns the Display to the Season Odometer.

ENGLISH/METRIC SWITCH

The English/metric switch located on the Instrument Cluster allows the driver to have speed and distance information displayed English or Metric values. This English/metric switch also has an output to the Driver Information System (DIS) and Heater and A/C Control Assembly (C68 only). With the Instrument Cluster English/metric switch in metric, this output is grounded. With this switch in English the output is pulled up to 5 volts by the Instrument Cluster. The DIS also has an English/metric switch, but it has no effect on the Instrument Cluster or the Heater and A/C Control Assembly displays.