21-44-00
 SENSE RELAY  ú ú 04 Page 5 ú Jan 28/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL

 G20758
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH AFT CARGO FAN CURRENT ú

 21-44-00
 SENSE RELAY  ú ú 02 Page 6 ú Jan 28/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757 MAINTENANCE MANUAL
 AFT CARGO COMPARTMENT HEATING SYSTEM - ADJUSTMENT/TEST
______________________________________________________
 1.  General_______
 A.  This procedure contains two tasks. The first task is an operational test of the aft cargo compartment heating system. The second task is a system test of the aft cargo compartment heating system.
 B.  The aft cargo compartment heating system includes a fan, an electric heater, ducting and outlets, controls (temperature switch, fire control module, relays, and current sensor), and EICAS displays.
 TASK 21-44-00-715-001
 2.  Operational Test - Aft Cargo Compartment Heating System_______________________________________________________
 A.  General
 (1)  
When the cargo compartment temperature is less than 50°F (10°C) the temperature control switch closes. This sends a signal to the relays that control the fan and heater. When the compartment temperature is 70°F (21°C) the switch opens the circuit to the cargo compartment relays. After a 20-second time delay, the fan relay stops the heat supply to the cargo compartment.

 B.  
Equipment

 (1)  
Cooling source - ice pack - commercially
 available.

 (2)  
Thermometer, 0 to 100°F (0 to 49°C),
 commercially available.

 C.  
References

 (1)  
06-46-00/201, Entry, Service and Cargo Doors, Access Doors and Panels

 (2)  
24-22-00/201, Electric Power-Control

 D.  
Access

 (1)  
Location Zone
 822 Left Cargo Compartment Door

 E.  
Test - Aft Cargo Compartment Heating System (Fig. 501)

 S 865-002
 (1)  
Make sure these circuit breakers on the overhead circuit breaker panel, P11, are closed:

 (a)  
11N1, INSTRUMENT AND PANEL AISLE STAND

 (b)  
11N18, CARGO HEAT AFT

 (c)  
11N22, CARGO HEAT FAN AFT

 (d)  
11S15, AIR/GND SYS 1

 (e)  
11S19, AIR/GND SYS 2

 (f)  
EICAS circuit breakers (5 locations)

 S 865-004
 (2)  
Make sure this circuit breaker on the miscellaneous electrical equipment panel, P70, is closed:

 (a)  
70C8, AFT CARGO HTR

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-44-00
 ALL  ú ú 02 Page 501 ú Jun 20/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757
MAINTENANCE MANUAL

FIRE SWITCH AFT CARGO 
rr 1-BTL DISCH-2 AFT ARMED FWD ARMED  E R I F O R G A C  a APUDISCH APU BTL DISCH  r 
a DISCH  a DISCH 
P8 PANEL 
SEE  A  APU/CARGO FIRE CONTROL PANEL 
FLT COMPT  AFT CARGO  A 

AFT CARGOHEATING INTAKE DUCT (REF) FLOW FAN
.
AFT CARGO HEATER SEE B
GRILL (REF)
WIRE FILTER (REF)
TEMPERATURE CONTROL SWITCH
AFT CARGO TEMPERATURE
CONTROL SWITCH

B
Aft Cargo Compartment Heating System Test Components Figure 501
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-44-00
 ALL  ú ú 04 Page 502 ú Sep 20/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL