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737-300/400/500MAINTENANCE MANUAL
(d) Move the ISOLATION VALVE switch to OPEN.
S 865-295
(8) Start the APU (AMM 49-11-00/201).
NOTE: The electrical load is to be less than 25 amperes.
____
S 865-296
(9) Set the APU BLEED switch on the P5-10 panel to ON.
(a) Make sure the duct pressure is more than 35 psi.
S 865-298
(10) Move the RECIRC FAN switch to OFF, on the P5-10 panel.
E. Procedure
S 715-342
(1) Do these steps to find the initial APU EGT (Left Pack):
(a)
Make a record of the ambient air temperature.
(b)
Set the APU bleed switch to OFF.
(c)
Look at the AC ammeter for the APU generator on the APU control panel. 1) Make sure the load on the APU generator is less than 25
amps.
NOTE: The electrical power should be supplied to the
____ airplane by a ground cart. If the APU supplies the electrical power the generator will have too much load.
2) Write down the exhaust gas temperature (EGT) for the APU, as Temperature #1.
NOTE: Let the APU EGT become stable for 2-3 minutes before
____ you write down the temperature. You can hit the temperature indicator lightly to remove the hysteresis. Make sure that the air mix valves stay at the full COLD position.
(d) Put the APU BLEED switch to the ON position.
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737-300/400/500MAINTENANCE MANUAL
(e) Move the L PACK and R PACK switches to HIGH.
NOTE: The APU EGT will increase.
____
S 715-343
(2) Do these steps to make sure the APU load control valve does not affect this operational test (Left Pack):
(a)
Set the R PACK switch to OFF.
(b)
Make sure that APU EGT decreases.
NOTE: This will make sure that the pack flow is controlled
____ by the Pack Flow Control and Shutoff Valve and not by the APU Load Control Valve. If the ambient temperature is more than 100°F, APU load limiting can occur normally and the APU EGT could not decrease. Do not continue to do this test if the pack flow is controlled by the APU Load Control Valve.
(c)
If the APU EGT does not decrease, do these steps: 1) Look at the right pack flow control and shutoff valve to make sure that the valve is fully closed.
2) Look at the left pack flow control and shutoff valve to make sure it moved to an intermediate position.
(d)
If these things have not occurred, do the Pack Flow Control and Shutoff Valve Test.
NOTE: The EGT may not decrease if there is leakage in the APU
____ duct, the APU bleed valve, the wing TAI valve, the PRSOV, or the air conditioning ducts. To see if there is a leak in the system, switch the APU bleed valve to OFF. If the EGT decreases, there was a leak.
S 715-339
(3) Do this check of the water separator (Left Pack):
(a) Disconnect the electrical connector, D710, from the 35°F control sensor on the left water separator.
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737-300/400/500MAINTENANCE MANUAL
(b) Make sure that the left 35°F control valve moves to the full open position as shown by the visual indicator on the valve.
NOTE: If the 35 degree F control valve does not move to
____ the full open position, then there is a problem with the valve or the wiring.
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