Electric Speedometer
The electric speedometer drive is standard equipment. Integrated circuits control the following components:
| • | The air core speedometer |
| • | The stepper motor odometer |
Lighting is provided by removable bulb and socket assemblies. The bulb and the socket assemblies insert into the back of the instrument cluster.
The speedometer system consists of the following components:
| • | The instrument cluster |
| • | The Vehicle Speed Sensor (VSS) |
| • | The Vehicle Control Module (VCM) |
| • | All related wiring |
The one-piece instrument cluster mounts in front of the driver in the instrument panel. The one-piece instrument cluster is not serviceable by the dealer. If the instrument cluster malfunctions, replace the instrument cluster. Only authorized instrument cluster service centers may perform repairs to the instrument cluster.
The VCM converts the analog output from the VSS to a digital signal. The digital signal contains 4000 pulses per mile (PPM) for the instrument cluster. The VCM is matched to the following specifications for each vehicle:
| • | The final drive axle |
| • | The tire size |
If the final drive axle or tire size is changed for any reason, update the VCM in order to match the new final drive axle or tire size. If the VCM is not matched to the drive axle or tire size, the signal will not be accurate for proper speedometer/odometer operation. An incorrect signal may affect antilock brakes and cruise control systems.
Tachometer
An optional tachometer indicates the engine speed in revolutions per minute (RPM) when the ignition switch is in the RUN position.
Fuel Gauge
The fuel gauge indicates the quantity of fuel in the tank when the ignition switch is in the RUN position. The pointer may rest at any position when the ignition switch is turned to any of the following positions:
| • | OFF |
| • | LOCK |
| • | START |
| • | ACC |
The fuel gauge measures the current from a variable resistor inside the fuel tank. A float inside the fuel tank controls the variable resistor. The resistance is high under the following conditions:
| • | The fuel tank is full. |
| • | The ignition switch is in the RUN position. |
When the resistance is high, the fuel gauge indicator moves to the maximum position or FULL on the gauge face.
When the fuel tank is empty, the resistance is low. The fuel gauge indicator then moves to the minimum position or EMPTY on the gauge face.
The following conditions generally cause the indicator to register past FULL on the gauge face:
| • | Corroded connections |
| • | Severed ground paths |
Short circuits to ground generally result in the indicator resting below EMPTY on the gauge face.
Coolant Temperature Gauge
When the ignition is in the RUN position, the coolant temperature gauge measures the current from a variable resistance sensor in the engine coolant jacket. The sensor changes resistance with the temperature of the coolant. When the coolant temperature increases, the resistance of the sensor decreases.
Oil Pressure Gauge
When the ignition switch is in the RUN position, the oil pressure gauge indicates the engine oil pressure. An oil pressure sender in the engine block changes resistance with the oil pressure.
Voltmeter
The voltmeter indicates nominal electrical system voltage. When the engine is running, the indicator should read between 10 and 16 volts.
The voltmeter has a red band at each extreme end of the voltmeter's range. During normal operation, the indicator rests between the red bands. If the indicator rests inside either red band, a charging system problem is indicated.
