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747-400 MAINTENANCE MANUAL
 (3)  S 755-045Make sure the drain mast becomes warm.
 (4)  S 865-016Open 414M32, DRAIN MAST HTRS GND MODE circuit breaker on the P414, Left Power Distribution Center.
 (5)  S 755-050Make sure the drain mast starts to become cool.
 S 865-018

 CAUTION:_______DO THE SUBSEQUENT 4 STEPS IN LESS THAN 5 MINUTES. THERE CAN BE DAMAGE TO THE DRAIN MASTS IF THEY OPERATE IN HIGH POWER MODE FOR TOO LONG.
 (6)  
Close 414M32, DRAIN MAST HTRS GND MODE circuit breaker on the P414, Left Power Distribution Center.

 S 865-019

 (7)  
Open 414C21, DRAIN MAST HTRS GND SVCE MODE circuit breaker on the P414, Left Power Distribution Center.

 S 755-053

 (8)  
Make sure the drain mast quickly becomes hot.

 S 865-021

 (9)  
Open these circuit breakers on the P414, Left Power Distribution Center:

 (a)  414L23, DRAIN MAST HTR AIR CTR
 S 755-054
 (10)
 Make sure the drain mast starts to cool.

 S 865-023

 (11)
 Close these circuit breakers on the P414, Left Power Distribution Center in this sequence:

 (a)  
414C21, DRAIN MAST HTRS GND SVCE MODE

 (b)  
414L23, DRAIN MAST HTR AIR CTR

 S 755-055
 (12)
 Make sure the drain mast becomes warm.

 S 865-025

 (13)
 Close these circuit breakers:

 (a)  
P7, Overhead Circuit Breaker Panel 1) 7F22, LANDING GEAR DSP & CONT PRI 2) 7F23, LANDING GEAR DSP & CONT ALTN

 (b)  
P180, DC Power Distribution Panel 1) 180J12, GND PWR SENSE

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 S 445-026
 (14) Do this task:  "Put Safety-Sensitive Systems Back to the Condition before Air Mode Simulation" (AMM 32-09-02/201).
 H. Ribbon Heaters Test
 S 015-027
 (1)  
Remove the applicable floor panels from the cargo compartment to get access to the ribbon heater thermostat.

 S 485-000

 (2)
Connect a clamp-on ammeter around one of the two heater lead wires.

 S 715-027

 (3)  
Do a check of ribbon heater operation:

 (a)  Make the heater thermostat cool with dry ice or freon spray.
 NOTE: To use the freon spray, apply the spray to the
____ thermostat for 2 seconds. After 5 seconds apply the spray again. Do this procedure as many times as necessary to make the thermostat sufficiently cool.
 (b)  
Make sure that the current is 0.075 amps or more.

 (c)  
As an alternative method to the current measurement, feel the ribbon heater with your hand to make sure that it is warm.

 S 085-028
 (4)  
Remove the clamp-on ammeter.

 S 415-031

 (5)  
Install the floor panels in the cargo compartment.

 I. Heated Supply Hose Test
 S 015-032
 (1)  
Remove the applicable cargo liners or floor panels to get access to the thermostat of the heated supply hose (AMM 25-52-01/401).

 (2)
Connect a clamp-on ammeter around one of the two heater lead wires.

 S 715-029

 (3)  
Do a check of the heated supply hose:

 S 485-030
 (a)  Make the thermostat cool with dry ice or freon coolant (the thermostat is located adjacent to the terminal end of the hose).
 NOTE: To use the freon spray, apply the spray to the
____ thermostat for 2 seconds. After 5 seconds apply the spray again. Do this procedure as many times as necessary to make the thermostat sufficiently cool.
　
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