Instrument Panel, Gauges and Warning Indicators: Description and Operation
DESCRIPTIONWhen the ignition switch is in "START" or "RUN", the gauges and several indicators are powered by fuse 17 through the 640 (R/Y) wires.
The instrument cluster gauges include the following: fuel, oil, temperature, and tachometer (optional). Each gauge consists of 2 coils, a magnet and a pointer, which moves in direct proportion to the output of its sender.
When the gauges are powered, a magnetic field is produced. The field varies in direction and strength according to the resistance of the sender.
COMPONENTS
Fuel Gauge And Fuel Gauge Sender
The fuel gauge sender's resistance controls the fuel gauge's pointer position. The sender has a resistance of 145 ohms when the fuel tank is "FULL" and 22.5 ohms when the fuel tank is "EMPTY".
Coolant Temperature Gauge And Sender
The coolant temperature sender's resistance controls the coolant temperature gauge's pointer position. The sender provides 74 ohms of resistance when the engine coolant is "COLD"and 9.7 ohms when the engine coolant is "HOT".
Oil Pressure Gauge And Oil Pressure Switch
The oil pressure switch controls the oil pressure gauge's pointer position. The oil pressure switch closes under normal engine operating conditions; the oil pressure switch opens with the engine off and no oil pressure.
Tachometer (optional)
The tachometer is an electrically operated gauge that indicates engine speed in rpm. The tachometer receives its voltage pulses from the ignition coil when the engine is running.
Voltmeter
With the ignition switch in "START" or "RUN", the voltmeter measures voltage to indicate the battery state of charge.
Programmable Speedometer/Odometer Module
The programmable speedometer/odometer module includes the speedometer, the odometer, and the trip odometer, all of which are electronically controlled by a programmable integrated microprocessor. The microprocessor receives a speed signal input from the Differential Speed Sensor (DSS), and uses a programmed conversion constant to convert the signal to the standard 8000 pulses per mile speed signal output. The programmable speedometer/odometer module is serviceable only as a unit. It is important to keep the speedometer face-up, since speedometer function will be affected by storage in the facedown position.