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757 MAINTENANCE MANUAL
I. Initial Insulation Resistance Check
S 486-062
(1)
Do this procedure: Calibrate the QuadTech Model 1864 Megohmmeter.
S 766-063
(2)
RESISTANCE CHECK WITH THE FUEL PUMP REMOVED FROM THE AIRPLANE; (optional) Do these steps to do a check of the insulation resistance:
(a)
Remove the fuel pump unit(s) (AMM 28-22-03/401).
(b)
Do this procedure on the removed pumps, within two hours: Final Insulation Resistance Check.
S 766-047
CAUTION:_______DO THE RESISTANCE CHECK AT 10 VDC FIRST. THE FUEL PUMPS ARE IN FLAMMABLE LEAKAGE ZONES. EACH PUMP IS TESTED AT 10 VDC BEFORE IT IS TESTED AT 500 VDC. THE INITIAL 10 VDC CHECK IS TO FIND OUT IF A FUEL PUMP HAS LOW INSULATION RESISTANCE WHICH CAN ARC OR OVERHEAT WHEN A HIGH VOLTAGE IS APPLIED. THE RESULTS OF THE 10 VDC CHECK WILL TELL YOU IF IT IS SAFE TO DO THE 500 VDC CHECK ON THE FUEL PUMP INSTALLED ON THE AIRPLANE.
(3) RESISTANCE CHECK WITH THE FUEL PUMP INSTALLED ON THE AIRPLANE; Do these steps to do a check of the insulation resistance (initial check).
NOTE: These steps are done at 10 VDC to prevent arcing or overheat
____ in a flammable leakage zone when high voltage is applied to a pump with low insulation resistance.
(a)
Do this procedure: Calibrate the QuadTech Model 1864 Megohmmeter.
(b)
Disconnect the electrical connector from the pump unit.
WARNING: MAKE SURE THE QUADTECH MODEL 1864 (OR EQUIVALENT)
_______ MEGOHMMETER IS USED TO MEASURE THE INSULATION RESISTANCE. IF NOT, IT IS POSSIBLE THAT AN EXPLOSION OR FIRE CAN OCCUR.
(c) Do these steps to connect the QuadTech Model 1864 megohmmeter for the 10 VDC check: 1) Plug the megohmmeter into a grounded receptacle. 2) Connect the +UNKNOWN probe to the pump connector pin 4
(ground). 3) Connect the -UNKNOWN probe to the pump connector pin 1. 4) Set the multiplier dial to the lowest range (100K). 5) Set the TEST VOLTAGE switches to 10V. 6) Set the measure switch to the MEASURE position.
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757
MAINTENANCE MANUAL
(d) Do these steps to measure the resistance at the applicable pump: 1) Turn the multiplier switch until the meter reading is less
than 5.
NOTE: The resistance is the meter reading multiplied by
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