Subaru 1600 Service Manual page 711

• Fuel Gauge
1) Specifications
Resolving power of
indication
Hysteresis of indication
Indicant mode
Low fuel warning light
2) Operation
ELECTRICAL SYSTEM
10 segments, about 6 liters (1.6 US gal, 1.3 Imp
gal) per segment
About 3 liters (0.8 US gal, 0.7 Imp gal)
c::=:::::J
0
c=:::J
c::=:::::J
c::=:::::J
c::=:::::J
c::=:::::J 0
c::=:::::J 0
=::::::J
=::::::J
=::::::J
c::=:::::J
=::::::J t:=::::J
c::=:::::J
0
t:=::::J 0
c::::::::J
0
"Full tank"
1/2 remaining
"Empty"
indication
fuel
indication
A25·778
Fig. 15-151
NOTE:
Even if fuel tank is empty, the lowest segment
light will not go out.
When "Empty" [about 6 liters (1.6 US gal, 1.3
Imp gal)] is displayed, orange low fuel indica-
tor light comes on.
A constant current of 27.S rnA flows
in the slide resistor of the fuel gauge
unit from the constant-current power
source. A change in the resistance of
Constant-current
Integrator
*
J
~
~ AID converter
power source
circuit
?
Fuel gauge
unit
* AID converter:
-=
Analog/digital converter
(A device converting analog output
signals into digital pulse signals.)
3) Indicant standards
Input standard
No. of illuminant
resistance
n
segments
10 10
62
5
99 ± 2 2-+1
As resistance rises (fuel decreases).
15-48
I ' ,
the slide resistor, caused by a change
in the fuel level, is converted into a
voltage variation; it passes through an
integrator circuit to eliminate voltage
fluctuation due to small waves in the
fuel level. After its conversion into
a digital signal by *the AID converter,
it is processed by the microcomputer
and indicated in a bar graph on the
fluorescent display tubes.
When the fuel decreases so much that
only the lowest segment lights, the
low fuel indicator light under the fuel
gauge illuminates. [The remaining
quantity of fuel is about
6
liters
(1.6 US gal, 1.3 Imp gal) at that time.]
NOTE:
The fuel level is measured by the fuel
gauge unit float. If waves suddenly
develop in the fuel tank due to motion
of the vehicle, the segments that have
gone out may illuminate again. This is
in no way a sign of any abnormality.
Likewise, the low fuel indicator light
that has gone out may light up again.
The light remains illuminated when
the fuel has decreased below 6 liters
(1.6 US gal, 1.3 Imp gal).
r--
Micro-processor
Display circuit
Bar graph
fluorescent
display tubes