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747-400
MAINTENANCE MANUAL

 (d)  
Make sure the left and right heaters are on (feel for increase in temperature of the airflow from the left and right heat ducts or feel for heat at the duct immediately downstream of each heater).

 (e)  
Apply heat source to temperature switch or allow time for the temperature of the forward cargo compartment to increase to more than 50°F (10°C).

 (f)  
Make sure the heaters are off (feel for decrease in temperature of the air that flows from the heat ducts).

 (g)  
Release the N2 Eng 1 and Eng 3 Ch 2 test switches.

 (h)  
If applicable, remove the heat source from the temperature switch and install the coverplate on the box.

 (i)  
Close these circuit breakers on the P6 main power distribution panel. 1) 6C33 AOA HEAT L 2) 6C34 AOA HEAT R 3) 6D28 PROBE HEAT TAT L 4) 6D29 PROBE HEAT TAT R 5) 6D30 PROBE HEAT PITOT L 6) 6D31 PROBE HEAT PITOT R 7) 6D32 PROBE HEAT AUX PITOT L 8) 6D33 PROBE HEAT AUX PITOT R 9) 6D34 PROBE HEAT IND L 10) 6D35 PROBE HEAT IND R 11) 6H19 PROBE HEAT ENG 1 12) 6H23 PROBE HEAT ENG 3

 S 865-011
 (5)  
Set the EQUIP COOLING switch on the P5 overhead panel to NORM

 (6)  
Remove electrical power if it is not necessary (AMM 24-22-00/201).

 S 865-005
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747-400 MAINTENANCE MANUAL
 FORWARD CARGO COMPARTMENT HEATER - REMOVAL/INSTALLATION
_______________________________________________________
 1.  General_______
 A.  There are two tasks in this procedure. There is one task for the removal and one task for the installation of the forward cargo compartment heaters. The procedure has these parts:
 (1)  
The removal of power to the heater

 (2)  
The removal of a ball transfer panel to get access to the heater

 (3)  
The removal of the heater

 (4)  
The installation of the heater

 (5)  
A system test of the forward cargo compartment heating system.

 B.  There are two forward cargo compartment heaters. The heaters are installed in the equipment cooling exhaust ducts. The procedure is the same for the left or the right heater.
 C.  The heaters are installed below the forward cargo compartment floor, between the station 600 and 620 body frames.
 TASK 21-43-01-004-001
 2.  Forward Cargo Compartment Heater Removal (Fig. 401)________________________________________
 A.  References
 (1)  
25-53-15/401, Ball Transfer Panel

 (2)  
IPC 21-43-52 Fig. 1

 (3)  
WDM 21-43-11

 (4)  
SSM 21-43-01

 B.  Access
 (1)  Location Zone 121 Forward Cargo Compartment Forward Half, LH 122 Forward Cargo Compartment Forward Half, RH
 C.  Procedure
 S 864-002
 (1)  Open these circuit breakers and attach DO-NOT-CLOSE tags:
 (a)  
P6 Main Power Distribution Panel
 1) 6F32 FWD CARGO HEAT CONT

 (b)  
P414 Power Distribution Center-Left
 1) 414J2 CARGO HTR PWR LEFT FWD

 (c)  
P415 Power Distribution Center-Right. 1) 415G18 CARGO HTR PWR RIGHT FWD

 S 014-004
 (2)  
Remove the center ball transfer panel from the forward cargo compartment floor (Ref 25-53-15/401).

 S 034-005

 (3)  
Remove the electrical connector from the heater:

 (a)  The right heater electrical connector DH526.
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