TM 1-1520-238-T-7
Change 5
10–155
10–48. FUEL QUANTITY SYSTEM – CAPACITANCE AND INDICATING TEST (cont)
10–48
(USING TF-579 TEST SET)
1. Perform fuel quantity system capacitance and indicating test as follows:
Task
Result
a. On pilot instrument panel, check that fuel
quantity indicator (fig. 10–63) edge-lights
are lighted.
If pilot fuel quantity indicator edge-lights are not
lighted, refer to TM 1-1520-238-T-5 to troubleshoot
engine instruments.
b. On CPG instrument panel, check that
selectable digital display (fig. 10–65)
edge-lights are lighted.
If selectable digital display edge-lights are not lighted,
refer to TM 1-1520-238-T-5 to troubleshoot engine
instruments.
NOTE
To prevent heat damage to digital instrument light segments, the test circuit
automatically opens (lamp out) two seconds after being switched on. To recycle
test mode release switch, wait one second, and reset TST switch to TST.
c. On dim/test panel (fig. 10–66), set DGT
OFF/NORM/TST switch to TST. Check pilot
fuel quantity indicator. All lamp segments
are lighted (2 seconds), and digital readout
is 888.
If all lamp segments are not lighted, replace lamps
(TM 1-1520-238-23). If lamps is still not lighted,
and/or digital readout is not 888, refer to
TM 1-1520-238-T-5 to troubleshoot engine
instruments.
d. On CPG selectable digital display, push and
hold TEST pushbutton. Check that digital
readouts indicate 888, then release TEST
pushbutton.
If digital readouts do not indicate 888, refer to
TM 1-1520-238-T-5 to troubleshoot engine
instruments.
NOTE
Prior to connecting the adapter harness (fig. 10–68) to the aircraft fuel quantity
wiring harness, the open capacitance of the adapter harness tank and indicator
leads must be measured and recorded using the fuel quantity test set.
e. Calibrate fuel quantity gage test set and
perform adapter harness capacitance
check(TM 1-1520-238-23).
f. On pilot ELEC PWR panel (fig. 10–69), set
BATT/EXT PWR switch to OFF.
