Cessna 1969-1976 172 Series Service Manual page 236

15 -42. TROUBLE SHOOTING. (C ont.
PROBABLE CAUSE
Loose
or
broken lead.
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TROUBLE
REMEDY
Check circuit wiring. Repair
or replace defective wiring.
EXCESSIVE POINTER
OSCILLATION. (Cont. )
Defective gage or sensing
unit.
Excessive panel vi bration.
Defective gage o r sensing
unit.
Defective m a s t e r switch.
Defective gage.
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~
~-
Substitute known-good gage
or
sensing unit. Replace gage
or
sensing unit.
Check panel shock-mounts.
Replace defective shock-mounts.
Substitute known-good gage
or
sensing unit. Replace gage or
sensing unit.
Replace switch.
Substitute known-good gage.
Replace gage.
OBVIOUSLY INCORRECT TEM-
PERATURE READING.
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POINTER FAILS TO GO O F F
SCALE WITH CURRENT O F F ,
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(15-43. FUEL QUANTITY SYSTEM.
15-44. DESCRIPTION. The magnetic type fuel quan-
tity indicators
are
used in conjunction with
a
float-
operated variable-resistance transmitter in each
fuel tank. The full position of float produces
a
mini-
mum resistance through transmitter, permitting
maximum current flow through the fuel quantity indi-
cator and maximum pointer deflection. A s fuel level
is lowered, resistance in transmitter is increased,
producing
a
decreased current flow through fuel quan-
tity indicator and
a
smaller pointer deflection.
115-44A. REMOVAL AND INSTALLATION.
a.
Drain fuel f r o m
tank.
(Observe precautions in
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Section 12.
SHOP NOTES:
b. Remove
access
plate above fuel tank for
access
c.
Disconnect
electrical
lead and ground s t r a p from
d. Remove
screws
attaching transmitter and
care-
e. Install transmitter by reversing preceding steps,
to transmitter.
transmitter,
fully work t r a n s m i t t e r f r o m tank. DO NOT BEND
FLOAT ARM.
using new gasket around opening in fuel tank and
under
screw
heads.
quantity indicator.
f. Service fuel
tanks.
Check f o r l e a k s and c o r r e c t
NOTE
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Ensure transmitter is properly grounded i n
accordance with Section 12.
15-18 Change 1