(a)  
Wheel well-wing-body-overheat (fire protection).

(b)  
Master warning and control (fire protection).

(c)  
Overheat (air conditioning).

(d)  
Master caution bus-1.

(e)  
Master caution battery bus.

(f)  
Indicator lights - Master dimming bus (nine circuit breakers).

(g)  
Dim and Test.

C.  Test System
(1)  
Press the overheat test switch on air conditioning module P5-10. The following lights should illuminate.

(a)  
Left overheat light (P5-10).

(b)  
Right overheat light (P5-10).

(c)  
Both master caution lights.

(d)  
Master caution air conditioning annunciator light.

(2)  
While holding test switch, position the lights test switch on the P2 panel to DIM and then back to BRT. The lights should dim and then return to their original brightness.

(3)  
Press either master caution light. The master caution lights and the air conditioning annunciator light should extinguish.

(4)  
Press the first officer's annunciator light panel. The master caution and air conditioning annunciator lights should again be illuminated.

(5)  
Release overheat test switch. The following lights should extinguish:

(a)  
Left overheat light on P5 panel.

(b)  
Right overheat light on P5 panel.

(c)  
Air conditioning annunciator light.

500 
Aug 15/67  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  26-18-0 Page 501 

NOTE:  Any other lights on annunciator or P5 panel that might be illuminated should be ignored when performing this test.
(6)  
Press either master caution light. Both master caution lights should extinguish.

(7)  
Determine whether there is any further need for electrical power on the airplane; if not, remove external power.

500 
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WING AND LOWER AFT BODY OVERHEAT DETECTION SENSING ELEMENT -REMOVAL/INSTALLATION

1.  General
A.  The following requirements must be met when installing a sensing element:
(1)  
Minimum element bend radius is 1 inch and optimum bend radius is approximately 3 inches.

(2)  
A minimum element straight run of 1 inch from all connectors and mounting clips is required prior to starting a bend. A straight run next to connectors shall be as long as possible.

2.  Equipment and Materials
A.  Bonding Meter (Ref 20-22-01)
B.  Lacing Tape-BMS13-54, Grade D, Type III, Class 1 Finish C or equivalent
3.  Remove Sensing Element (Fig 401,402)
A.  Open wheel well-wing-body-overheat circuit breaker on load control center P6.
B.  Disconnect electrical connector at either end of sensing element. Cover open end of electrical connectors with tape or suitable protective caps to ensure exclusion of dirt (Fig. 401).
C.  Start at one end and slip sensing element out of each mounting clip. Hold element carefully to prevent excessive bending.
D.  Remove jamnut from end fitting at each end of sensing element and remove element and end fittings from flange fitting. Cover open ends of end fittings with tape or suitable protective caps to ensure exclusion of dirt.
NOTE:  To facilitate installation and provide for proper routing of sensing element, sensing element being replaced may remain in approximate position supported by tubes and brackets in the area. Rubber bushings may be retained for use on new sensing element dependent on bushing condition.
NOTE:  Overheat sensing elements M370 and M371 may have short silicone tubes installed over the elements in critical locations to prevent false overheat annunciation. When removing these elements, discard the lacing tape and retain the silicone tube for re-installation, if it is serviceable.
E.  Remove sensing element by carefully working sensing element out from beneath tubing and brackets.
NOTE:  For ease of handling and disposition, carefully roll sensing element into a coil approximately 4 inches in diameter. Tape as necessary to retain coil shape.
500 
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H21788
Wing and Lower Aft Overheat Detection Sensing Element Installation  500 
26-18-11  Element Installation  Nov 15/69 
Page 402  Figure 401 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 
　
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