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A

747-400
MAINTENANCE MANUAL

FLOAT SWITCH FOR THE WING SURGE TANK
SEE A
FLOAT SWITCH FOR THE WING SURGE TANK
SEE A
FRONT SPAR
FILLET SEAL
(AROUND FLOAT
SWITCH FLANGE)

WASHER
(11 LOCATIONS)

O-RING
NUT (11 LOCATIONS)
ELECTRICAL
CONNECTOR,
DS690, DS691

FWD
FLOAT SWITCH, S690, S691
FLOAT SWITCH FOR THE WING SURGE TANK
A
Float Switch for the Wing Surge Tank
Figure 401

D14276
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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A
747-400
MAINTENANCE MANUAL

 B. Consumable Materials
 (1)  
A00256 Sealant, Integral Fuel Tank, BMS5-26, Type II

 (2)  
B00148 Solvent - Methyl Ethyl Ketone (MEK), TT-M-261

 (3)  
D00128 Petrolatum - Technical, VV-P-236

 (4)  
G00507 Cloth - Clean, lint-free

 C.
References

 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 27-81-00/201, Leading Edge Flap System

 (3)  
AMM 28-11-00/801, Fuel Tanks - Repair

 (4)  
AMM 28-21-12/501, Surge Tank Float Switch

 (5)  
AIPC 28-21-12 Fig. 1

 (6)  
SWPM 20-20-00, Electical Bond and Ground

 (7)  
SSM 28-21-01

 (8)  
WDM 28-21-11, 28-21-12

 D.
Access

 (1)  
Location Zones
 555 Surge Tank, Front Spar to Rear Spar, Left
 655 Surge Tank, Front Spar to Rear Spar, Right

 (2)  
Access Panel
 555AB Surge Tank Access Door
 655AB Surge Tank Access Door

 E.
Procedure

 S 114-026
 WARNING:  DO NOT GET SOLVENTS IN YOUR MOUTH, OR YOUR EYES, OR ON YOUR SKIN. DO NOT BREATHE THE FUMES FROM SOLVENTS. SOLVENTS ARE HAZARDOUS MATERIALS. SOLVENTS MAY BE FLAMMABLE OR HARMFUL TO THE ENVIRONMENT. REFER TO PRODUCT MATERIAL SAFETY DATA SHEETS (MSDS) AND LOCAL REQUIREMENTS FOR PROPER HANDLING PROCEDURES.
 (1)  
Apply MEK, Acetone, IPA, or Ethyl Alcohol to a lint-free cloth.

 S 114-035

 (2)  
Use the cloth with the MEK, Acetone, IPA, or Ethyl Alcohol to clean the mating surfaces of the float switch and airplane structure.

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MAINTENANCE MANUAL

 S 164-022

 (3)  
Use a dry cloth to dry the mating surfaces of the float switch and the airplane structure.

 S 644-036

 (4)  
Apply petrolatum to the new O-ring.

 S 434-011

 (5)  
Install the new O-ring on the switch flange.

 S 424-012

 (6)  
Put the float switch through the opening in the front spar.

 S 424-025

 (7)  
Install the flange on the bolts so that the switch is in the downward vertical position.

 S 434-013

 (8)  
Install the nuts and the washers (11 locations).

 S 764-015

 (9)  
Measure the bonding resistance between the float switch and the airplane structure (SWPM 20-20-00).

 NOTE: The bonding resistance must not be more than 0.010 ohm.
____
 S 394-037
 (10)
 Apply a pressure fillet seal around the edge of the float switch flange with the BMS5-26 Type II sealant (AMM 28-11-00/801).
　
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