501  Operational Test No. 2 (Optional) Adjustment 
Feb 01/74  Figure 503  77-21-0 
Page 507 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

EXHAUST GAS TEMPERATURE INDICATING SYSTEM (MILLIVOLT) - INSPECTION/CHECK
1.  Exhaust Gas Temperature Indicating System Check
A.  General
(1)  
Engine compartment cleanliness is important because the extensive mass air flow tends to draw foreign objects into the engine. Thoroughly clean the entire engine compartment with a vacuum cleaner after completion of any work. Keep the compartment and the annular duct free of dirt, oil and grease, and remove all unused parts, such as nuts, washers, and pieces of lockwire. Immediately cover all apertures resulting from the disconnection of parts. Use external caps on all openings, not internal plugs.

(2)  
Carefully check the exhaust gas temperature indicating system without dismantling to ensure that all connections are tight and that lines are secure.

B.  Check Thermocouple Probes and Harness
(1)  
Check for burned, broken or deformed probes.

(2)  
Check for chafed or broken wiring.

(3)  
Check continuity and insulation resistance of harness.

2.  Electrical Check of EGT System for 17A, Engines Incorporating Boost Circuit During Every Basic Hot Section Inspection (Fig. 601)
A.  Short Circuit Check
(1)  
Disconnect terminals at locations A, B, C, D and E in Figure 601.

(2)  
Set ohmmeter range switch to a range which has center scale value of approximately ten ohms.

(3)  
Place one prod in good contact with well-cleaned alumel terminal A and other in good contact with well-cleaned chromel terminal B. Flex cable gently and observe instrument needle. If any deflection results (unless caused by accidental contact between other terminals of cable), reject part.

5C8 
Jun 20/85  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  77-21-0 Page 601 

B.  Continuity Check
(1)  
Set ohmmeter range switch to a range, which has center scale value of approximately ten ohms.

NOTE:  Broken wires which come into contact intermittently due to flexing will cause needle to fluctuate. False intermittent indications will result if ohmmeter prods are not in firm contact with clean terminals; also, if ohmmeter prods, leads, or jacks are defective fluctuations can occur.

(2) Perform continuity check for each of the following thermocouple lead circuits:

(a)

(b)  
B to D *[1]

(c)

*[1]  Resistance of this circuit should be higher than that of other two because of integral fixed resistor.
NOTE:  While performing continuity check, gently flex lead.
EGT System Boost Circuit Check  5C2 
77-21-0  Figure 601  Sep 20/82 
Page 602 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

P&WA 77-20 Page 603, 604, Apr. 1/82

(d)  Lead is unserviceable if high resistance (open circuit) is read on ohmmeter.
(3)  
Perform continuity check at the junction box for each of the following junction box and harness and lead assembly circuits (with probes attached):

(a)  
1 to J

(b)  
6 to J

NOTE: While performing continuity check, gently flex cable assembly.

(c)  
Junction box and harness and lead assembly, thermocouple probe No. 1 or 6 is unserviceable if high resistance (open circuit) is read on ohmmeter. Isolate problem per Section 77-21-01, I/C.

(4)  
Reconnect terminals at locations A, B, C, D and E.

(5)  
Perform continuity check from terminal A to B.

(6)  
If a high resistance (opens circuit) is read on ohmmeter, system is unserviceable. If lead was serviceable per steps (2) thru (4), isolate the discontinuity by testing the thermocouple cable assembly per Section 77-21-01, I/C.

5C2 
Sep 20/82  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  77-21-0 Page 603 

P&WA 77-20 Page 604, 605/606, Apr 1/82
C.  Isolation Resistance Check See Figure 601.
(1)
Ensure that the thermocouple cable and leads are properly installed and connected.

NOTE:  Insulation resistance values slightly below the limits set forth below may not result in a deficient EGT system. It does, however, clearly indicate that the insulation is deteriorating and will result in eventual shorts or erroneous EGT readings. Therefore, EGT system components with insulation resistance readings below the limits set forth require attention to restore the insulation resistance to acceptable values and prevent further deterioration and possible EGT system failure.
　
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