Fuel Gauge

The magnetic fields of the 2 coils moves the pointer of the fuel gauge. The coils are at right angles to each other. The E-coil (empty) supplies the battery voltage. The circuit divides at the opposite end of the coil. One path continues to ground through the F-coil (full). Another path goes to ground through the variable resistance of the level sensor in the fuel pump and sender. When the tank is low, the resistance of the level sensor is low. A large current flow passes through the E-coil. The pointer moves toward E on the fuel gauge. When the tank is full, the fuel level sensor resistance is high. Less current passes through the E-coil. The pointer moves toward F on the scale. With 2 coils operating the pointer, changes in the system battery voltage does not affect the fuel gauge.

The fuel level sender operates in a range from around 40 ohms when the tank is empty and a 250 ohms when the tank is full. If the VCM receives a signal from the fuel level sender either higher or lower than the specified range it will automatically send a signal to the fuel gauge to show empty.

The fuel gauge does not operate in the same range as the sender. When the signal is sent to the VCM it is modified to a 0 ohms to 90 ohms scale. When it sees 0 ohms at the VCM it shows empty. When it sees 90 ohms it shows full.