(4)
If the wires do have any sign of electrical arcing and there is no copper wire showing, then you can re-use the old float switch.
(5)
If you find locations on the wires where the insulation has wear, then you must replace the float switch with a new one before 15,000 flight hours (SB 28-1132),
(6)
The insulation has wear if you can see a dent or low spot in the insulation.
(7)
If you will re-use the old float switch, then do this test of the switch insulation:
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.
(a)
Remove the insulation from the ends of the float switch wires.
(b)
Temporarily connect the ends of the two float switch wires together.
(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, they 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 outer cover or the threaded end of the switch.
(8)
Measure the resistance between the wires and the float switch housing at 500 VDC.
(a)
If the resistance is less than 200 megohms, then you must replace the float switch.
(b)
Disconnect the megohm meter from the float switch and disconnect the two float switch wires from each other.
(9)
Apply Proseal 860 sealant to the top of the float switch.
(a)
Apply a small quantity of the sealant with a brush.
(b)
Put it on the area where the anodized layer was broken by the probe tips.
(c)
Refer to AMM 28-11-0/801 for data on how to apply sealant.
(10)
Use compressed air (30 psi maximum) to blow dirt out of the conduit.
(11)
Do these steps to install a TFE-2X14SW Teflon sleeve over each wire of the float switch (one wire per sleeve):
CAUTION: DO NOT SHRINK THE TEFLON SLEEVE WITH HEAT. HEAT CAN CAUSE DAMAGE TO THE INSULATION ON THE WIRE.
(a) Cut two pieces of TFE-2X14SW sleeve to the correct length of 18 feet.
Sep 01/02 28-21-71 Page 605
(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. 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 this steps: a) Cut the sleeve so that about one inch 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.
(12) Do these steps to install a TFE-2X6TW Teflon sleeve over the two TFE-2X14SW sleeves (one sleeve with both wires in it):
CAUTION: DO NOT SHRINK THE TEFLON SLEEVE WITH HEAT. HEAT CAN CAUSE DAMAGE TO THE INSULATION ON THE WIRE.
(a)
Cut a piece of TFE-2X6TW sleeve to the correct length of 18 feet.
(b)
Do these recommended steps to install the sleeve: 1) Push a wire (referred to as the fish wire), such as lock wire or a stiff electrical
wire, through the TFE-2X6TW sleeve. 2) Use the fish wire to pull two strings through the TFE-2X6TW sleeve. 3) Tie one string to each TFE-2X14SW sleeve.
NOTE: The knot shown in Figure 603 is recommended
NOTE: If you are re-installing the old float switch, then start the knot at a location that will be about 3 inches outside of the conduit on the airplane. Use the mark you made before you removed the wire from the airplane to find this location
4) Pull one of the float switch wires and its TFE-2X14SW sleeve through the TFE-2X6TW sleeve with the string. a) Pull until the TFE-2X14SW sleeve touches the sleeve that is a part of the
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