Fuel level sensor — check (VW Golf 1)

The fuel level sensor in the fuel tank consists of a float and an electrical resistor. When the ignition is turned on, the indicator in the panel receives voltage. The variable resistance in the sensor closes the current circuit. The sensor makes a connection "to ground". Depending on the amount of current that flows in the system, the bimetallic plate in the indicator heats up more or less strongly. Accordingly, the arrow fixed to it deflects. When the float is in its highest position with a full tank, the resistance at the fuel sensor is shunted; the bimetallic plate is fully heated and allows the pointer to fully deflect. When the tank contents have decreased, the float drops; because of this, the higher resistance reduces the current to the bimetallic strip; the arrow points to a smaller quantity.

Possible malfunctions

There may be the following reasons for incorrect readings.



If the level is too high or too low, then the voltage stabilizer is defective or the float arm is bent.

If there is no reading, then the fuel sensor or indicator is defective. If there is no fuel and temperature reading or the readings are incorrect, the cause may be a faulty voltage stabilizer. This must be determined accurately.

Adjusting the fuel level sensor

If the readings are incorrect due to a bent float, the fuel sensor must be removed.

When the float arm bends upward, the reading decreases; when bending downwards, the reading increases.

Checking the fuel sensor

Open access to the sensor. Remove the wires.

Connect the wires together.

Turn on the ignition briefly. If the arrow deviates towards "Voll" ("Full"), then the fuel level sensor is defective.

If the arrow does not move, then either the purple-black wire leading to the instrument panel is open, or there is a defect in the board or in the indicator.

For information on checking the pointer, see the section "Instructions for checking devices" this chapter.