Testing fuel gauge sender — AUDI

ABZ ACK AEJ AEM AEW AGE AGH AHC AKB AKC AKD AKG AKH AKJ ALG AMX APR AQD AQF AQG AQH ARU AUW AUX AVN AVP AYS AZC BCS
Special tools and workshop equipment required

V.A.G 1526 A

V.A.G 1594 A

Notes:

Testing signal from fuel gauge sender:

=> Electrical system; Repair group 90
Electrical system

Fuel tanks installed in A8 vehicles with 6-cylinder can have a nominal capacity of either 80 or 90 litres. They can be distinguished by means of the 6-digit production number next to the manufacturer's identification stamp: e.g. 656694. The first digit of this number indicates the tank capacity as follows:
1st digit 6:
80 litre tank;
1st digit 0, 8 or 9:
90 litre tank.
Fuel tanks supplied as replacement parts always have a capacity of 90 litres.
Observe safety precautions => Page
20-2
.
Before removing the two fuel gauge senders, use an ohmmeter to check whether the resistance values of the senders correspond with the fuel gauge reading. The two senders are wired in series, so the two resistance values must be added together in order to check the fuel gauge reading.

Checking resistance values of fuel gauge senders (two senders)

Remove covers for fuel gauge senders and fuel delivery unit on left and right sides under floor covering in boot -arrows-.

Release 4-pin connector -arrow- and unplug.

Connect multimeter to contacts 2 and 3 on right-hand sender (resistance test range)

Release and unplug 2-pin connector on left-hand sender.
Connect multimeter (resistance measurement range) between contacts 1 and 2.
Add the resistance values of the two senders together and compare with the following table.

Notes:

The left-hand chamber of the tank is always drained first.
When the tank is 1/4 full, you should therefore obtain a resistance of 80 ... 100 ω at the right-hand sender and a resistance of 40 ... 44 ωat the left-hand sender.
A resistance of 40 ... 44 ωat the left-hand sender means that the left-hand chamber is completely empty.

80 litre fuel tank · 90 litre fuel tank
Fuel gauge reading · Resistance / ω · Content / / litres · Resistance / ω · Content / / litres
Empty · 166 ± 7 · 0 · 166 ± 7 · 0
Res. 1 1) · 154 ± 7 · 12 · 154 ± 7 · 12
1/4 · 136 ± 7 · 20 · 131 ± 7 · 22
1/2 · 94 ± 6 · 39 · 88 ± 6 · 42
1/1 2) · 21 ± 4 · 79 · 12 ± 4 · 87
1/1 3) · 19 ± 4 · 84 · 9 ± 4 · 92

1)
Fuel gauge needle on first graduation in reserve zone

2)
Fuel gauge needle exactly in line with top graduation

3)
Fuel gauge needle above top graduation

Note:

In order to test the maximum and minimum values for "tank full" and "tank empty", remove both fuel gauge senders => Page
20-126
, and pivot or slide the floats of the two senders all the way to their top and bottom positions.

When the fuel gauge sender is removed, the float will travel further and the specifications are:

Sender · Sender at top position · Sender at bottom position
Fuel gauge sender -G / (at fuel delivery unit) · approx. / 4.4 ω · approx. / 125 ω
Fuel gauge sender 2 / -G169 (left side) · approx. / 5.8 ω · approx. / 45 ω