S 766-017
WARNING:_______DO NOT DO THIS TEST ON OR NEAR THE AIRPLANE. THIS TEST USES HIGH VOLTAGES THAT CAN MAKE A SPARK. IF YOU ARE NEAR THE AIRPLANE, THE SPARK CAN CAUSE IGNITION OF FUEL VAPORS.
(6) If you will re-use the old float switch, then do this test of the switch insulation:
(a)
Remove the insulation from the ends of the float switch wires.
(b)
Temporarily connect the ends of the two float switch wires together.
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A 737-300/400/500MAINTENANCE MANUAL
(c) Connect a megohm meter between the ends of the wires and the
float switch housing.
NOTE: Make sure the probe tips from the meter go through _____
the anodized layer on the float switch housing. If the
probe tip does not go through the anodized layer and
touch the aluminum, then you will not get the correct
measurement.
1) You must connect to the part of the housing that is a bump
in the center of the top of the float switch
2) Do not connect to the outer cover or the threaded end of
the switch.
(d) Measure the resistance between the wires and the float switch
housing at 500 VDC.
1) If the resistance is less than 200 megohms, then you must
replace the float switch.
(e) Disconnect the megohm meter from the float switch and
disconnect the two float switch wires from each other.
(f) Apply Proseal 860 sealant to the top of the float switch.
1) Apply a small quantity of the sealant with a brush.
2) Put it on the area where the anodized layer was broken by
the probe tips.
3) Refer to AMM 28-11-00/801 for data on how to apply the
sealant.
S 146-025
(7) Use compressed air (30 psi maximum) to blow dirt out of the conduit.
S 426-026
CAUTION:_______DO NOT SHRINK THE TEFLON SLEEVE WITH HEAT. HEAT CAN CAUSE DAMAGE TO THE INSULATION ON THE WIRE.
(8) Do these steps to install a TFE-2X14SW Teflon sleeve over each wire of the float switch (one wire per sleeve):
(a)
Cut two pieces of TFE-2X14SW sleeve to the correct length of 11 feet (3.4 meters).
(b)
It is not possible to push the wires on the float switch through the sleeve. It is recommended to do these steps to install the sleeves: 1) Push a wire (referred to as the fish wire), such as lock
wire or a stiff electrical wire, through the TFE-2X14SW sleeve. 2) Tie the float switch wire to the fish wire with a string. a) It is recommended that you use the knot shown in Figure 603.
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A 737-300/400/500MAINTENANCE MANUAL
3) Pull the float switch wire through the TFE-2X14SW sleeve with the fish wire. a) Pull until the TFE-2X14SW sleeve touches the sleeve
that is a part of the float switch.
NOTE: This is easiest with two people, one to pull
____ the fish wire, and the other to hold the opposite end of the sleeve.
4) If the float switch wires are shorter than the sleeve, then do these steps: a) Cut the sleeve so that about one inch (25.4 millimeter)
of wire shows, at the free ends of the wire. 5) Push the sleeve farther on the wire, until you can remove the string. 6) Remove the string from the wire, and pull the sleeve back up the wire.
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