Fuel Gauge Adjustment

[kirby.a.smith@lmco.com]

Audinauts

Having just made some repairs to my wife's 1988 90q instrument panel, 
(a trace broke some time ago on someone else's watch and the repair 
they selected was to solder a wire between two panel illumination 
lamps; said wire breaking and revealing its presence by the loss of 
the right half of the panel illumination), I can answer a question 
that appeared in this forum a couple of weeks ago.  {please excuse the 
Dickensonian sentence.}  The information below strictly applies only 
to 1988 90qs with the trip computer, but I expect it is of general 
application to a wider range of Audis.

Adjusting the fuel gauge and the trip computer fuel range adjustment 
are two steps performed with the same control.  To adjust the fuel 
gauge, a 149.5 ohm resistor is put across the connector that connects 
to the fuel tank sensor, after disconnecting the connector.  The plug 
in the end of the shaft protruding only slightly from the instrument 
panel next to the fuel gauge is pulled and a tool such as a No. 1 
Phillips screwdriver is used to engage this shaft, turn it, and thence 
the fuel gauge needle via some internal gears.  The needle center is 
to be aligned with the right edge of the third large tic mark from the 
empty position.

For the trip computer, a very narrow but long screwdriver is needed.  
I made a special tool from a heavy gauge coat hanger wire, cutting out 
an 8-inch section, and grinding one end to resemble a flat blade 
screwdriver.  This blade is inserted into the hole through the center 
of the shaft described above and used to turn a mini-potentiometer 
that is mounted at the back of the instrument panel.  (One could get 
to this from below, probably.)  With a full (!) tank, turning the 
ignition on while holding the trip computer reset button down and 
having the function pointer on miles (or km),should yield the display 
of a number specified in the Bentley by model.  (650 for 90 quattros)  
The potentiometer is adjusted to make the display show the specified 
value.

Anyone with a dark right half instrument panel should contact me for 
hints on a likely trace break location.

***                 ...Kirby    (Kirby A. Smith)                 ***
***                      2 X 1988 90q                            ***
***              ksmith1@mailgw.sanders.lmco.com                 ***
***              [=]   kirby.a.smith@lmco.com                    ***
***  Opinions expressed herein are entirely those of the author. ***