(1)  
Put the AC motor into position against the outflow valve.

 (2)  
Install the screws in the AC motor.

 S 424-017
 S 434-016
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757 MAINTENANCE MANUAL
 S 434-015
 (3)  
Connect the electrical connector to the AC motor.

 D.  
Do the AC motor installation test.

 S 864-014
 (1)  
Remove the DO-NOT-CLOSE tags and close these circuit breakers, on the P11 panel:

 (a)  
11B14, CABIN ALTITUDE CONTROL MANUAL

 (b)  
11B15, CABIN ALTITUDE CONTROL SELECT

 (c)  
11N15, CABIN ALTITUDE CONTROL AUTO 1

 (d)  
11N24, CABIN ALTITUDE CONTROL AUTO 2

 S 864-013
 (2)  
Supply the electrical power (AMM 24-22-00/201)

 S 714-012

 (3)  
Do the AC motor installation test procedure.

 (a)  
Remove the DO-NOT-OPERATE tag and turn the MODE SELECT selector, on the P5 panel, to MAN.

 (b)  
Turn and hold the MANUAL selector, on the P5 panel, to DESCEND until the outflow valve is fully closed.

 (c)  
Turn the MODE SELECT selector, on the P5 panel, to AUTO 1.

 1)  Make sure the outflow valve moves to the full open position.

 (d)  
Turn the MODE SELECT selector, on the pilots P5 panel, to MAN.

 (e)  
Turn and hold the MANUAL selector, on the P5 panel, to DESCEND until the valve is fully closed.

 (f)  
Turn the MODE SELECT selector, on the P5 panel, to AUTO 2.

 1)  Make sure the outflow valve moves to the full open position.
 E.  Put the airplane back to its usual condition.
 S 414-011
 (1)  
If you installed the AC motor from the bulk cargo compartment, do the steps that follow:

 (a)  
Install the aft endliner in the bulk cargo compartment (AMM 25-50-03/401).

 (b)  
Close the aft cargo door, 822 (AMM 06-46-00/201).

 S 864-010
 (2)  Remove the electrical power if it is no longer neccessary
 (AMM 24-22-00/201).

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757 MAINTENANCE MANUAL
 PRESSURE RELIEF VALVES - DESCRIPTION AND OPERATION
__________________________________________________
 1.  General_______
 A.  The pressurization relief valves provide cabin pressure relief from extreme cabin-to-ambient differential pressure, if the pressurization system malfunctions (Ref 21-31-00), or in the event of a rapid emergency airplane descent.
 B.  Two positive pressure relief valves act independently of each other to prevent excessive positive cabin-to-ambient differential pressure by opening at 8.95 psi differential. The valves are mounted flush with the airplane skin, aft of the left wing-to-body fairing.
 C.  Two vacuum relief valves act independently of each other to prevent negative cabin-to-ambient differential pressure from exceeding 0.75 psi by opening at 0.3 psi differential. The valves are mounted flush with the airplane skin on the right hand side, forward of the No. 1 cargo door.
 2.  Component Details_________________
 A.  Positive Pressure Relief Valve (Fig. 1)
______________________________
 (1)  
The positive pressure relief valve is a pneumatically-operated poppet valve. The valve mounts directly on the fuselage skin aft of the left wing-to-body fairing. The valve discharges cabin air directly overboard when high cabin-to-ambient differential pressures exist. The relief valve limits the cabin-to-ambient differential pressure by controlling airflow through the poppet. The relief valve's head pressure (same as cabin pressure) controls poppet motion. Airflow through a metering section controls the head pressure. When the differential pressure sensed by the metering section approaches 8.95 psi, the metering pin lifts off its seat, releasing head pressure overboard through a dump tube. This opens the valve to reduce cabin pressure.
　
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