(5)  
Remove the bulkhead union O-ring.

5.  AIRPLANES WITH TYPE I FLOAT SWITCH; Install the Fueling Float Switch
A.  Slip washers and mounting nut on float switch wires and install loosely on switch. Place switch in fuel tank.
(1)  737-200 AIRPLANES WITHOUT VOLUMETRIC TOP-OFF UNITS;
For the fueling float switch in the center tank, do these steps:

CAUTION:  AIRCRAFT FLOAT SWITCH WIRING MAY EXHIBIT EXCESSIVE WEAR ON CENTER TANK.
(a)  
Make sure the necessary Teflon sleeve is installed on the float switch wire bundle before you pull the wiring through the conduit (SB 737-28-1132).

(b)  
Do an inspection of the wiring and the conduit (AMM 28-21-71/601).

(c)  
Install or re-install the Teflon sleeving if it is necessary (AMM 28-21-71/601) (SB 737-28-1132).

B.  If the conduit of the fueling float switch found in the wing tank was removed, do the steps that follow:
(1)  
Put a new O-ring on the bulkhead union.

(2)  
From in the wing tank, put the bulkhead union through the wing front spar.

(3)  
Make sure the bulkhead union aligns with the union retainer fitting.

(4)  
From out of the wing tank, install the washer on the bulkhead union.

NOTE:  Make sure the bulkhead union is held from in the wing tank while the bulkhead union washer and nut are installed. This is to prevent the union from falling in the wing tank.

(5)  
Install the bulkhead union nut.

(6)  
From in the wing tank, loosely install the conduit nut on the bulkhead union.

C.  Attach wire puller to float switch wires and pull wires through conduit until ends extend out through bulkhead fitting on front wing spar. Use care to prevent kinks in wire or damage to insulation.
WARNING:  DO NOT ATTEMPT TO SHORTEN FLOAT SWITCH WIRES TO LOCATE SPLICE WITHIN CONDUIT. AN EXPLOSION HAZARD COULD RESULT IF SPLICE DEVELOPS AN ELECTRICAL SHORT
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D.  Inside fuel tank, drop mounting nut and one of the two washers down on float switch wires. Guide wires through slot in mounting bracket and position threaded base of switch in bracket (Fig. 401).
NOTE:  On some center tank installations, it is only necessary to loosen mounting nut. Bracket slot is wide enough to accommodate threaded base of float switch.
E.  Install washer and nut. Ensure that a washer is positioned on upper and lower surface of mounting bracket.
F.  Restrain switch from turning to prevent twisting wires while nut is tightened. Secure nut with lockwire.
G.  Connect electrical conduit to float switch and secure conduit nut with lockwire.
H.  If the conduit was removed, do these steps:
(1)  
From in the wing tank, tighten the conduit nut at the bulkhead union.

(2)  
If loosened, tighten the conduit union connection.

(3)  
Secure the conduit nut at the bulkhead union with lockwire.

(4)  
Secure the conduit union connection with lockwire.

(5)  
From out of the wing tank at the wing front spar, tighten the bulkhead union nut.

I.  Fuel Conduit Fill Procedures (Applicable to wing tanks No. 1 and No. 2 only)
(1)  
Get a flexible tube with a 0.25 inch (or smaller) outer diameter. There is one available in either fuel conduit fill kit. Put marks on the tube at 14, 16, and 17 inches from one end.

(2)  
At the bulkhead fitting (Fig. 401), push the tube into the conduit approximately 16 inches.

NOTE:  The end of the tube can catch on the edge of the union at 14 inches. Push it past this point. The tube can stop at the 16 inch point. If possible, push the tube past this low point in the conduit. Continue to push it around the elbow bend to a maximum depth of approximately 17 inches. This is recommended as it will permit more grease to be put into the conduit.

(3)  
Use a dispensing gun to add the MIL-G-27617 Type I grease. This grease is available in either fuel conduit fill kit. Put the grease through the tube into the airspace in the conduit. Continue adding the grease until it comes out the end of the conduit.

(4)  
Slowly remove the tube while adding more grease. This will keep the conduit completely filled. It will also prevent air voids in the conduit.

NOTE: MIL-G-27617 Type II, III, IV greases are suitable substitutes for Type I grease.
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May 01/03  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  28-21-71 Page 407 

J.  Outside fuel tank, slip the rubber grommet (installed on wing tank float switch), nylon grommet and conduit nut over end of float switch wires and install on end of bulkhead fitting on front wing spar (Detail A, Fig. 401).
　
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