(2)  
Main engine bleed valves

(3)  
Thermal anti-icing valves

(4)  
Tire seal valves (on airplanes with inflatable tire seal)

(5)  
APU bleed air valve

C.  Open circuit breaker C404, LANDING GEAR LIGHTS, Panel P6-2. Verify that surge bleed valve has opened by noting increased air flow from APU accessory cooling air exhaust port.
NOTE: Increased air flow should be accompanied by increased EGT and noise level.
D.  Position APU bleed air valve switch to ON. Note lower noise level and decreased air flow at cooling air exhaust port, indicating surge bleed valve closure.
E.  Close circuit breaker C404, panel P6-2 and position APU bleed air valve switch to OFF.
F.  Shut down APU - Engine Shutdown Procedure (Ref 49-11-0, Maintenance Practices).
500 
Sep 20/82  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-52-41 Page 501 

THERMOSTAT SELECTOR SOLENOID VALVE - REMOVAL/INSTALLATION
1.  Prepare for Thermostat Selector Solenoid Valve Removal
A.  Position BATTERY SWITCH and APU START SWITCH to OFF and placard.
B.  Open circuit breaker on M280 module, APU accessory unit on E3-3 electronic shelf.
C.  Open APU compartment access door latches and open door. Install door support rods.
D.  Support lower shroud, open shroud latches, and remove shroud.
CAUTION:  EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
2.  Remove Thermostat Selector Solenoid Valve (Fig. 401)
A.  Disconnect electrical plug from thermostat selector solenoid valve.
B.  Disconnect air lines (three) from fittings engaging thermostat selector solenoid valve. Tag identify as an aid for reconnecting.
C.  Remove two bolts, nuts and washers securing solenoid valve to bracket and remove valve.
D.  Remove fittings. Remove and discard packings.
500 
Aug 01/74  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-52-61 Page 401 

3.  Install Thermostat Selector Solenoid Valve (Fig. 401)
A.  Install new packings on fittings and install fittings in thermostat selector solenoid valve.
B.  Install bolts, nuts and washers and secure thermostat selector solenoid valve to mounting bracket. Tighten nuts to torque value of 20-25 pound-inches.
C.  Connect air lines to fittings in thermostat selector solenoid valve. Remove, if used, identification tags.
D.  Connect electrical plug to thermostat selector solenoid valve and safety wire.
4.  Restore Airplane to Normal Configuration
A.  Position lower shroud against upper shroud and close shroud latches.
CAUTION:  MAINTAIN A MINIMUM CLEARANCE OF 0.18 INCH BETWEEN ENGINE PLUMBING, FIRE DETECTOR, CLAMPS AND INSIDE SURFACE OF LOWER SHROUD.
EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
B.  Disengage APU access door support rods and stow rods. Close and latch access door.
C.  Close the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.
D.  Position BATTERY SWITCH to ON and remove placards.
501 
49-52-61 Page 402  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/76 

551  Thermostat Selector Solenoid Valve - Installation 
Aug 01/75  Figure 401 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-52-61 Page 403 

APU OVERTEMPERATURE CONTROL THERMOCOUPLE - REMOVAL/INSTALLATION
1.  Equipment and Materials
A.  Antiseize Compound - Fel-Pro C-5A, Felt Products Corp., Skokie, Illinois
2.  Prepare for Thermocouple Removal
A.  Position BATTERY SWITCH and APU START SWITCH to OFF and placard that APU maintenance is "in work."
B.  Open the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.
C.  Open APU compartment access door latches and open access door.
D.  Support lower shroud, open shroud latches, and remove shroud.
CAUTION:  EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
3.  Remove Thermocouple (Fig. 401)
A.  Disconnect electrical connector from overtemperature control switch and remove clamps securing thermocouple cable to tube assemblies.
B.  Remove retainer attaching bolt, washers, and retainer.
C.  Remove thermocouple in a straight line from mount flange.
D.  Remove grommet and pull thermocouple through exhaust baffle.
4.  Install Thermcouple
　
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