The deviation of the needle of the fuel quantity indicator is changed by contact with the ground. This is provided by the fuel level sensor, which, depending on the filling of the fuel tank, has a higher or lower resistance. The voltage supply and signal preparation for the fuel level sender is provided by the combined instrument panel's central microprocessor. Information on dismantling the fuel level sensor can be found in chapter Fuel tank and fuel pump.
Malfunctions in the operation of the fuel quantity indicator
High or low readings: fuel level sensor float incorrectly installed (see next section), or no amendments have been made (V.A.G 1551).
No reading: The incoming voltage is out of range of the combined instrument panel, or the level sensor or indicator is defective.
Faulty fuel gauge or fuel level sensor?
1. Expose the fuel gauge wire connectors (chapter Fuel tank and fuel pump), disconnect the multi-pin connector.
2. Connect the auxiliary wire to the purple/black wire connector and apply directly to ground.
3. Briefly turn on the ignition.
4. If the indicator arrow deviates completely, then the lead wire and the indicator itself are in order. Then the fuel level sensor remains the cause of the malfunction.
5. If the arrow stays in position «empty», then there is a fault in the supply wire, in the wire of the combined instrument panel or in the fuel gauge. The fuel level sensor is probably ok.
Checking and adjusting the fuel gauge
1. Uncover connectors of wires of the gauge of level of fuel.
2. Disconnect the connector and measure the resistance on the fuel level sensor connector with an ohmmeter:
3. Tank full: 40 ohms.
4. Tank half full: 115 ohms.
5. Tank reserve: 250 ohm.
6. If the obtained measurement results are completely different from the specified ones, then: the fuel level sensor is faulty.
7. If the measurement results are in order, but the readings of the fuel quantity indicator have a large error or there is no indication, then: there is no conductivity or the device is faulty.
8. The measurement results are close or the indicator is inaccurate: the float of the fuel level sensor is incorrectly adjusted.
9. Installing the float of the fuel level sensor: this is a job for the workshop, which can make adjustments using the VAG 1551 error reader. Within certain limits, the following can be done:
10. Remove the fuel level sensor.
11. If the fuel quantity indicator overestimates the data, then: slightly bend the float lever up.
12. If the fuel gauge is low, then: slightly bend the float lever down.
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