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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL

PRECOOLER CONTROL VALVE
Precooler Control Valve Schematic Figure 3
C96743
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A
737-300/400/500MAINTENANCE MANUAL
 C.  Duct overheat protection is provided by an overheat (thermal) switch located downstream of the precooler but upstream of the precooler control valve sensor (Ref Fig. 2). If the sensed temperature at the switch exceeds 490 (| 10)°F the switch closes, causing the pressure regulator and shutoff valve to close and energizing the appropriate trip-off light on the flight crew's panel. The pressure regulator and shutoff valve is also controllable from the flight deck and may be reset in flight after a trip-off, once the overheat switch has cooled and reopened.
 D.  Ground wing thermal anti-ice (WTAI) solenoid valve operation is initiated by actuating the WTAI control switch on the P5 overhead panel to ON when the bleed air system is on and the airplane is on the ground. The solenoid valve, which is installed in the sense line from the precooler control valve to the precooler valve sensor, is energized to the open position and will vent the control fuctions of the precooler control valve thus causing the valve to drive full open. The solenoid valve remains open as long as the WTAI switch is ON and the airplane is on the ground. The valve will close if the WTAI switch is positioned OFF or the airplane leaves the ground. The valve will remain off during flight.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 BLEED AIR PRECOOLER - REMOVAL/INSTALLATION
__________________________________________
 1.  General_______
 A.  This procedure has four tasks. The first task removes the bleed air precooler with the engine removed. The second task installs the bleed air precooler with the engine removed. The third task removes the bleed air precooler with the engine installed. The fourth task installs the bleed air precooler with the engine installed.
 B.  The bleed air precooler is used to decrease the temperature of the bleed air supplied to the main manifold. It is found above the core section of the engine and is attached to the engine strut. It is not necessary to remove the engine to replace to the precooler on the engine. However, it is much easier to replace the precooler with the engine removed.
 TASK 36-12-25-004-044
 2.  Bleed Air Precooler Removal (With Engine Removed)___________________________
 A.  References
 (1)  AMM 71-00-02/401, Engine Power Plant
 B.  Access
 (1)  Location Zones
 501 Engine No. 1
 502 Engine No. 2

 C.  Prepare to Remove the Precooler
 S 024-056
 (1)
Remove the engine power plant from the strut (AMM 71-00-02/201).

 (2)  
Disconnect the sense line from the pressure port on the precooler.

 S 034-109

 (3)  
Remove the supports for the sense line and wire bundle from the precooler.

 S 034-107
 (a)  Move the sense line and wire bundle away from the precooler.
 D.  Remove the Precooler (Fig. 401)
 S 024-049
 (1)  Remove the coupling between the bleed air exhaust port of the precooler and the interface for bleed air duct at the nacelle strut firewall.
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