Fuel Quantity Sender Resistance Limits; 9-8A. Checking Fuel Quantity Senders - Piper Navajo PA-31 Service Manual

PIPER NAVAJO SERVICE MANUAL
d. Turn the master switch ON and observe the fuel quantity gauge. It should read
empty with the respective fuel selector lever at both the inboard and outboard ON
positions.
e. Add fuel to each cell in the amount of 10.0 U.S. gallons to the outboard cell and
14.0 U.S. gallons to the inboard cell, to bring each cell to one-quarter its full capacity.
f.
Again move the selector lever to both ON positions and observe the gauge. At either
position the quantity pointer should align with any part of the gauge index wire.
g. Continue to add fuel in increments of 10.0 and 14.0 U.S. gallons to the outboard
and inboard cells respectively for each quarter capacity of the cells. At each quarter
increment, until full, check that the quantity pointer aligns with any part of the index wire,
with the selector lever at either ON position.
h. Should the gauge and the amount of fuel in the cell not correspond, the gauge may
be calibrated per paragraph 9-9.
9-8a. CHECKING FUEL QUANTITY SENDERS.
a. Disconnect the sender unit and check for the ohm readings noted in Table IX-I.
TABLE IX-I. FUEL QUANTITY SENDER RESISTANCE LIMITS
Unit Location
Float Position
Ohm Reading
Main & Auxiliary Inboard
Empty
0 to 0.5
Full
48 to 52
Main & Auxiliary Outboard Empty
0 to 0.5
Full
38 to 42
Main & Optional Nacelle
Empty
0 to 0.5
Full
28 to 32
b. The sender unit must be replaced if the above tolerances are not maintained.
9-9. ADJUSTMENT OF FUEL GAUGES. The fuel gauges have been calibrated at time of
installation at the factory and normally need not be recalibrated unless a gauge or cell
sender unit has been replaced. Should it become necessary to calibrate a gauge, the
following procedure may be used:
CAUTION
Adjust the quantity gauge; do not try to change adjustments
of the sender units.
a. Accomplish the preparatory procedure as given in paragraph 9-8, steps a thru c and
read note.
b. Lower the overhead panel that houses the fuel gauges. Do not disconnect the
electrical wires.
Revised: 3/11/81 FUEL SYSTEM
3B2