Gauges

When the ignition is in RUN or START battery voltage is supplied through fuse 13 to the gauges in the gauge assembly.


Engine Coolant Temperature Gauge


The engine coolant temperature (ECT) gauge is operated by two intersecting coils wound around a permanent magnet rotor. When voltage is applied to the coils, a magnetic field is generated which causes the rotor to rotate and the gauge needle to move. The magnetic fields are controlled by the engine coolant temperature (ECT) sending unit. As the resistance in the sending unit varies, current through the gauge coils changes, and the gauge needle moves according to the changing magnetic field.


Fuel Gauge


The fuel gauge is operated by two intersecting coils wound around a permanent magnet rotor, and a bucking coil in series with the full coil. When voltage is applied to the coils, a magnetic field is generated which causes the rotor to rotate and the gauge needle to move. The magnetic fields are controlled by the fuel gauge sending unit in the fuel tank unit. As the resistance in the sender varies, current through the gauge coils changes, and the gauge needle moves according to the changing magnetic field. When you turn the ignition OFF, the needle remains at the last reading until you turn it ON again.


Tachometer


The tachometer driver in the gauge assembly controls the tachometer. With the ignition in RUN or START the tachometer driver receives pulses from the powertrain control module (PCM). The powertrain control module (POM) determines the engine speed from the crank-cylinder sensor. The number of pulses per minute is proportional to engine speed. The tachometer driver converts those pulses to movement of the tachometer needle.


Speedometer and Odometers


With the ignition in RUN or START the trip/total odometer driver and the speedometer driver in the gauge assembly are supplied battery voltage through fuse 13. The trip/total odometer driver applies voltage to the speed input terminal (YEL/RED wire). The vehicle speed sensor (VSS) creates a pulsing in the YEL/RED wire by switching its connection to ground on and off. The number of pulses increases as speed increases. The trip/total odometer driver uses this input to drive the trip and odometer stepper motors, and also supplies it to the speedometer driver to control the speedometer.