Prizm L4-1800cc 1.8L DOHC (1993)
Fuel Gauge: Description and Operation
CIRCUIT OPERATION
The pointer of the Fuel Gauge is moved by the magnetic fields of two coils. The coils are at right angles to each other. Voltage is applied to coil F
from the GAUGE Fuse through the Audio Alarm Module and Junction Block 3 when the ignition switch is in the "ON" or "START" position. The
circuit divides at the opposite (ground) side of the coil. One path seeks a ground through coil E and the other path seeks a ground through the
variable resistor in the Fuel Gauge Sending Unit.
When fuel level is low, resistance in the Fuel Gauge Sending Unit is high. Since current will always seek the path of least resistance, current will
flow through the F coil and the E coil to ground at G202. Since the length of the E coil winding is twice the length of the F coil winding, the
magnetic field generated by coil E is twice as strong as the magnetic field generated by coil F. Therefore, the pointer will be pulled to the "E"
position.
As fuel level rises, resistance in the Fuel Gauge Sending Unit decreases. Since current will always seek the path of least resistance, more current
will begin to bypass the E coil and travel directly to ground through the Fuel Gauge Sending Unit. Under these conditions, the coil F magnetic
field becomes stronger than the coil E magnetic field and the pointer moves toward the "F" position.
