Overtemperature Control Switch Test 501
49-52-81 Figure 501 Feb 20/86
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Feb 01/96 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-52-81 Page 503
G01897
Overtemperature Control Switch Adjustment 501
49-52-81 Figure 501 (Sheet 1) Feb 20/86
Page 504
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
501 Overtemperature Control Switch Adjustment
Feb 20/86 Figure 502 (Sheet 2) 49-52-81
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(18)
Apply one drop sealing component to overtemperature control adjustment screws and adjoining surface. Reinstall end plate and secure with screws.
(19)
Disconnect flexible line from bulkhead fitting on tail pipe heat shield.
(20)
Reconnect control air line to APU control thermostat and bulkhead fitting.
(21)
Check overtemperature control switch system operation (See par. 2., Steps B. thru G).
(22)
Remove test thermocouple assembly and reinstall engine thermocouple and connect thermocouple wiring.
(23)
Disconnect test temperature indicator from receptacle J3 of overtemperature control switch and reinstall cap on J3 receptacle.
(24)
Cap and stow all parts of thermostat calibration kit.
4. Overtemperature Control Switch Deactivation
A. There are two circumstances which can require deactivation of the overtemperature control switch:
(1)
Operation of the overtemperature control switch is erratic or fails to close the APU bleed valve;
(2)
The APU being installed is replacing an APU that has had the overtemperature control switch deactivated.
B. Deactivate the APU control switch as follows:
(1)
Overtemperature Control Switch Deactivation (Preferred Method).
(a)
Shut down APU (AMM 49-11-0/201).
(b)
Remove connector from receptacle J2 of the overtemperature switch.
(c)
Extract pins B and D from the connector.
(d)
Cut wires from pins B and D and discard pins.
(e)
Strip and splice the two wires together using an insulated splice (NAS 1388).
(f)
Tape or tie wires and replace connector on receptacle J2.
(g)
Start APU (AMM 49-11-0/201). Allow APU EGT to stabilize and switch APU bleed air to ON. Verify that pneumatic duct system is pressurized.
(2)
Overtemperature Control Switch Deactivation (Optional Method).
(a)
Shut down APU (AMM 49-11-0/201).
(b)
Tie back and cap the already disconnected overtemperature thermocouple wire and connector.
(c)
Fabricate a six inch jumper wire from BMS 13-31 Type 1, 18 gauge wire or equivalent.
(d)
Attach new contact points P/N BACC47DR1 to each end of jumper wire.
(e)
Insert jumper wire assembly into new plug BACC63BW10SLC4S (optional FRF6E10SL4501).
(f)
Install new plug with jumper wire at receptacle J1.
(g)
Start APU (Ref 49-11-0 MP). Allow APU EGT to stabilize and switch APU bleed air switch to ON. Verify that pneumatic duct system pressurized.
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C. Shut down APU - Engine Shutdown Procedure (Ref 49-11-0 MP).
D. Secure APU Compartment.
Table 1. Engine Exhaust Gas Temperature (EGT) Settings COMPRESSOR DISCHARGE PRESSURE ORIFICED TEE - CLEANING/PAINTING
EGT Measurement Pneumatic Thermostat Overtemperature Control Trip Point *[1]
Test Thermocouple Max640 + 10°C -5°C (1184 + 18°F -9°F) Recommended Max 620 ±10C (1150 ±20F) *[2] 718 +0 -14C (1325 +0 –25F)
*[1] Set overtemperature control trip point at recommended temperature only when pneumatic thermostat is set at recommended temperature.
*[2] The manufacturer recommends these lowered temperature settings to increase the service life of the engine “hot” section.
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Jun 20/86 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-52-81 Page 507
1. General
A. The following procedure permits a quick economical means of cleaning and assuring that the 0.030-0.034-inch diameter orifice is unobstructed without removing the orificed tee assembly from the engine.
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