500
77-21-31 Page 402 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Nov 15/69
EXHAUST GAS TEMPERATURE HARNESS AND LEAD - ADJUSTMENT/TEST
1. Exhaust Gas Temperature Harness And Lead Test
A. General
(1)
The exhaust gas temperature harness and lead is checked for evidence of mechanical damage to stainless steel braid, glass fiber sleeving, teflon coating (if so provided), and terminals. Check for rupture or severe fraying, and for broken conductor strands at any terminal.
(2)
Check mounting clips for deterioration of cushioning material. Replace defective clips.
(3)
The harness and lead is tested for continuity, insulation resistance and shorts with an ohmmeter. The validity of electrical checks made in the field may depend upon limitations inherent in the common ohmmeter. This instrument is not dependable for determining the exact wire resistances of the EGT harness and leads. However, it may be used to detect gross failures such as open or intermittent circuits and metal-to-metal short circuits. Also, approximate insulation resistance can be checked if certain precautions are observed. The ohmmeter used in the following test must be of good quality and in good condition; i.e. free from "stickiness" of the meter needle, with pin-jacks firm, test leads sound, and dry cells in condition to permit full scale deflection for all positions of the range switch.
B. Equipment and Materials
(1)
Sensitive Ohmmeter
(2)
Low voltage ohmmeter capable of measuring resistance of 50,000 ohms. Meter should utilize less than 40 volts (dc) and should have accuracy of 5 percent.
C. Prepare for Test
(1)
Check that thrust reverser is in forward thrust position to permit entrance into engine exhaust section.
(2)
Observe the following precautions for maintenance in engine exhaust section.
(a)
Pull applicable engine ignition circuit breaker on circuit breaker panel P6-2, and placard the circuit breaker with DO-NOT-CLOSE.
(b)
Placard thrust reverser controls with DO-NOT-OPERATE.
500
May 15/78 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 77-21-31 Page 501
WARNING: SERIOUS INJURY CAN OCCUR IF ENGINE IS STARTED AND/OR IF THRUST REVERSER IS OPERATED.
(3)
Enter engine exhaust section.
(4)
Remove 12 screws retaining duct cover ring to fan discharge turbine exhaust inner rear duct. Slide duct cover ring to the rear. Refer to Fan Discharge Ducts and Cases, Chapter 72.
(5)
Obtain access to EGT circuit connector or junction box and terminal strip by opening left cowl panel. EGT circuit connector or junction box is located at approximately the 7 o'clock position on the engine, and the terminal strip at approximately the 9 o'clock position.
(6)
On engines with EGT electrical connector, disconnect electrical connector. On engine equipped with a junction box, remove output leads, cover and bus bar.
(7)
Disconnect harness lead terminals from terminal strip.
Test Schematic 500
77-21-31Page 502 Figure 501 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Jun 20/89
D. Test Exhaust Gas Temperature Harness and Lead (Fig. 501 thru 503)
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