Functional Test of the Exhaust Gas Temperature (EGT) Harness, the Junction Box and the Thermocouples [IAE]

TASK 77-21-43-700-010-A
Functional Test of the Exhaust Gas Temperature (EGT) Harness, the Junction Box and the Thermocouples

WARNING: BE CAREFUL WHEN YOU DO WORK ON THE ENGINE PARTS AFTER THE ENGINE SHUTDOWN. USE APPLICABLE THERMAL GLOVES. THE ENGINE PARTS CAN STAY HOT FOR ONE HOUR AFTER SHUTDOWN AND CAN BURN YOU.

ZONE: 400
FIN: 1000EM1 ** ON A/C NOT FOR ALL
FIN: 1000EM2 ** ON A/C NOT FOR ALL

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	ACCESS PLATFORM 1M(3 FT)
No specific	AR	HOT AIR SOURCE
No specific	1	MEGOHMMETER - MODEL 1620-C
No specific	AR	MULTIMETER KEITHLEY MODEL 177
No specific	AR	NITROGEN COMPRESSED SOURCE - GROUND
No specific	AR	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
400	POWER PLANT, NACELLES AND PYLONS
FOR [1000EM1] (ENGINE-1)
437AL, 438AR, 451AL, 452AR
FOR [1000EM2] (ENGINE-2)
447AL, 448AR, 461AL, 462AR

C. Referenced Information

REFERENCE	DESIGNATION
TASK 71-13-00-010-010-A	Opening of the Fan Cowls 437AL(447AL),438AR(448AR)
TASK 71-13-00-410-010-A	Closing of the Fan Cowls 437AL(447AL),438AR(448AR)
TASK 77-21-15-400-010-A	Installation of the Exhaust Gas Temperature (EGT) Thermocouple
TASK 77-21-43-400-010-B	Installation of the Exhaust Gas Temperature (EGT) Harness and Junction Box (PRE SB 77-0015 and POST SB 77-0015)
TASK 78-30-00-040-012-A	Deactivation of the Thrust Reverser Hydraulic Control Unit (HCU) for Ground Maintenance
TASK 78-30-00-440-012-A	Re-activation of the Thrust Reverser Hydraulic Control Unit (HCU) after Ground Maintenance
TASK 78-32-00-010-010-A	Opening of the Thrust Reverser Halves
TASK 78-32-00-410-010-A	Closing of the Thrust Reverser Halves
EGT Harness and Junction Box (11625A)
EGT Harness and Junction Box (Thermocouple Locations) (11628B)
EGT Harness and Junction Box Test (11621)
EGT Harness and Junction Box - Drip Loop Connections to the Junction Box
EGT Harness and Junction Box Test (11622)
EGT Harness and Junction Box Test (11624)
EGT Harness
EGT Junction Box

3. Job Set-up
Subtask 77-21-43-941-051-A ** ON A/C NOT FOR ALL

A. Safety Precautions
(1) On the center pedestal, on ENG panel 115VU:
(a) Put a WARNING NOTICE(S) in position to tell persons not to start the engine.
(2) Make sure that the engine 1(2) shutdown occurred not less than 5 minutes before you do this procedure.
(3) On the overhead maintenance panel 50VU:
(a) Make sure that the ON legend of the ENG/FADEC GND PWR/1(2) pushbutton switch is off.
(b) Put a WARNING NOTICE(S) in position to tell persons not to energize the FADEC 1(2).

Subtask 77-21-43-010-051-A ** ON A/C NOT FOR ALL

B. Get Access
(1) Open the fan cowls (Ref. AMM TASK 71-13-00-010-010):
(a) FOR [1000EM1] (ENGINE-1)
437AL 438AR.
(b) FOR [1000EM2] (ENGINE-2)
447AL 448AR.
(2) Put the ACCESS PLATFORM 1M(3 FT) in the position.

Subtask 77-21-43-040-054-A ** ON A/C NOT FOR ALL

C. Deactivate the thrust reverser.

WARNING: MAKE SURE THAT THE THRUST REVERSER HYDRAULIC CONTROL UNIT (HCU) IS DEACTIVATED BEFORE YOU DO WORK ON OR AROUND THE THRUST REVERSER. IF THE HCU IS NOT DEACTIVATED, THERE IS A RISK OF UNWANTED THRUST REVERSER OPERATION WHICH CAN CAUSE INJURY TO PERSONS AND/OR DAMAGE TO EQUIPMENT.

(1) Deactivate the thrust reverser hydraulic control unit (HCU) (Ref. AMM TASK 78-30-00-040-012).

Subtask 77-21-43-010-057-A ** ON A/C NOT FOR ALL

D. Open the thrust reverser halves (Ref. AMM TASK 78-32-00-010-010):
(1) FOR [1000EM1] (ENGINE-1)
451AL 452AR.
(2) FOR [1000EM2] (ENGINE-2)
461AL 462AR.

Subtask 77-21-43-020-052-A ** ON A/C NOT FOR ALL

E. Disconnect the EGT harness.

EGT Harness and Junction Box (11625A) ** ON A/C NOT FOR ALL

EGT Harness and Junction Box (Thermocouple Locations) (11628B) ** ON A/C NOT FOR ALL

(1) Disconnect the harness from the thermocouples:
(a) Remove the nuts (17) and (19) and the washers (18) and (20) from the thermocouples.
(b) Disconnect the EGT harness from the thermocouples.
(2) Disconnect the harness from the junction box terminals

WARNING: USE PROTECTIVE GOGGLES AND GLOVES WHEN YOU REMOVE OR INSTALL LOCKWIRE. EACH TIME YOU CUT LOCKWIRE, REMOVE AND DISCARD IT IMMEDIATELY. LOOSE LOCKWIRE CAN CUT YOU OR MAKE YOU BLIND, AND/OR CAN CAUSE DAMAGE.

(a) Cut and discard the lockwire and remove the screws (7) which secure the junction box cover. Remove the cover.
(b) Remove the nuts (5) and (6) which secure the lugs of the harness (4) to the junction box terminals (2) and (3). Remove the harness lugs from the junction box terminals.
(c) Cut and discard the lockwire and remove the screws (9) which secure the harness clamps (10) and (13). Remove the clamps.

4. Procedure
Subtask 77-21-43-720-051-A ** ON A/C NOT FOR ALL

A. Test of the EGT Harness to Check for Continuity

EGT Harness and Junction Box Test (11621) ** ON A/C NOT FOR ALL

NOTE: The multimeter and the test leads must be in good condition. The dry cells must be in a condition to give full scale movement for all the positions of the range switch. Make sure that the pin jacks are tight.

NOTE: For POST SB 77-0012 EGT Harness, the continuity check test on the drip loops is not required.
For drip loops, see the sheet 1 of the figure.

EGT Harness and Junction Box - Drip Loop Connections to the Junction Box ** ON A/C NOT FOR ALL

ACTION	RESULT
1.Set the MULTIMETER KEITHLEY MODEL 177 or equivalent to the range that has a center scale value of approximately 10 ohms.
2.Do the continuity test of the EGT harness from the thermocouples to the junction box. If when you bend the wire, the resistance value changes, reject the harness.	The resistance value must be between 0 and 10 ohms. NOTE: There are four thermocouple locations with four leads at each location, which means that sixteen measurements are necessary.
3.If the meter shows a high resistance value, reject the harness.	Resistance value above 10 ohms

Subtask 77-21-43-820-050-A ** ON A/C NOT FOR ALL

B. Test of the EGT Harness for Short Circuits

EGT Harness and Junction Box Test (11622) ** ON A/C NOT FOR ALL

NOTE: For POST SB 77-0012 EGT Harness, the short circuit test on the drip loops is not required.
For drip loops, see the sheet 1 of the figure.

EGT Harness and Junction Box - Drip Loop Connections to the Junction Box ** ON A/C NOT FOR ALL

ACTION	RESULT
1.Set the MEGOHMMETER - MODEL 1620-C or equivalent to the 100VDC scale.
2.Put one lead of the meter in contact with the chromel harness lug by the A circuit. Put the second lead in contact with the alumel harness lug of the A circuit.	A resistance value of more than one megohm must show.
3.Put the second lead in contact with the chromel harness lug of the B circuit.	A resistance value of more than one megohm must show.
4.Put the second lead in contact with the alumel harness lug of the B circuit.	A resistance value of more than one megohm must show.
5.Put one lead of the meter in contact with the alumel harness lug of the A circuit. Put the second lead in contact with the chromel harness lug of the B circuit.	A resistance value of more than one megohm must show.
6.Put the second lead of the meter in contact with the alumel harness lug for the B circuit.	A resistance value of more than one megohm must show.
7.Put one lead of the meter in contact with the chromel harness lug of the B circuit. Put the second lead in contact with the alumel harness lug of the B circuit.	A resistance value of more than one megohm must show.
8.If the resistance value shown is less than one megohm or 0 ohm in one of these tests, reject the harness.

NOTE: Small movements of the harness during the tests must not cause the meter to move to below one megohm. This can be a sign of a defect and you must reject the harness.

Subtask 77-21-43-720-052-A ** ON A/C NOT FOR ALL

CAUTION: DO NOT ACCIDENTLY TOUCH THE INSULATION WITH THE INSTRUMENT PROBE.

C. Test of the EGT Harness and Junction Box for Insulation Resistance

EGT Harness and Junction Box Test (11624) ** ON A/C NOT FOR ALL

EGT Harness ** ON A/C NOT FOR ALL

EGT Junction Box ** ON A/C NOT FOR ALL

NOTE: For POST SB 77-0012 EGT Harness, the insulation resistance test on the drip loops is not required.
For drip loops, see the sheet 1 of the figure.

EGT Harness and Junction Box - Drip Loop Connections to the Junction Box ** ON A/C NOT FOR ALL

ACTION	RESULT
1.Set the megohmmeter to the 100VDC scale.
2.Put one lead of the meter in contact with the external steel braid of each harness lead. Put the other lead in contact with each of the output lugs of the junction box end of the harness.	A resistance value of more than one megohm must show.
3.If the resistance value shown is less than one megohm, correct or repair the harness. NOTE: The harness and junction box can absorb or trap moisture after water wash or an overnight in wet/humid conditions. High humidity can cause insulation resistance to read low. If insulation resistance reads low, you can apply hot air or nitrogen to correct this condition, or the harness can be restored by the bake procedure in the vendor CMM.
4.Do the test of the resistance between each junction box terminal stud and the junction box base. NOTE: Do not touch the insulation with the instrument probe.	A resistance value of more than one megohm must show.
5.If the resistance value is less than one megohm, reject the junction box. NOTE: The harness and junction box can absorb or trap moisture after water wash or an overnight in wet/humid conditions. High humidity can cause insulation resistance to read low. If insulation resistance reads low, you can apply hot air or nitrogen to correct this condition, or the harness can be restored by the bake procedure in the vendor CMM.
6.Do the test of the resistance between each separator band and the external steel braid of each circuit.	A resistance value of more than one megohm must show.
7.If the resistance value shown is less than one megohm, correct or repair the harness. NOTE: The harness and junction box can absorb or trap moisture after water wash or an overnight in wet/humid conditions. High humidity can cause insulation resistance to read low. If insulation resistance reads low, you can apply HOT AIR SOURCE or NITROGEN COMPRESSED SOURCE - GROUND to correct this condition, or the harness can be restored by the bake procedure in the vendor CMM.
8.Do the test of the resistance between the lug and the band separator of each circuit.	A resistance value of more than one megohm must show.
9.If the resistance value shown is less than one megohm, correct or repair the harness. NOTE: The harness and junction box can absorb or trap moisture after water wash or an overnight in wet/humid conditions. High humidity can cause insulation resistance to read low. If insulation resistance reads low, you can apply HOT AIR SOURCE or NITROGEN COMPRESSED SOURCE - GROUND to correct this condition, or the harness can be restored by the bake procedure in the vendor CMM.

Subtask 77-21-43-720-054-A ** ON A/C NOT FOR ALL

D. Loop Resistance Test on the EGT Thermocouples

ACTION	RESULT
1.Do the test on circuit A. NOTE: We recommend that you use clamps on the style probes to get accurate measurements.
a. Connect one of the leads to the alumel stud (larger diameter).
b. Connect the other lead to the chromel stud.
c. Measure and make a record of the resistance.
d. Interchange the leads.
e. Measure and make a record of the resistance.
f. Get the average of the two measurements.	The value must be between 0 and 3 ohms
g. If the value is more than 3 ohms, reject the thermocouple.
2.Do the test again on circuit B.

Subtask 77-21-43-720-055-A ** ON A/C NOT FOR ALL

E. Insulation Resistance Test on the EGT Thermocouple with a Megohmmeter

NOTE: Do this test on all four thermocouples.

ACTION	RESULT
1.Set the megohmmeter to the 100VDC scale.
2.Do a test of all circuits against each other and against non-circuit components.
a. Do a test for the insulation resistance between circuit A and the thermocouple casing.
b. Do a test for the insulation resistance between circuit B and the thermocouple casing.
c. Do a test for the insulation resistance between circuit A and circuit B.
d. If the resistance is less than 100 K ohms for any of the tests, reject the EGT thermocouple.

5. Close-up
Subtask 77-21-43-420-052-B ** ON A/C NOT FOR ALL

A. Connect the EGT harness.

EGT Harness and Junction Box (11625A) ** ON A/C NOT FOR ALL

EGT Harness and Junction Box (Thermocouple Locations) (11628B) ** ON A/C NOT FOR ALL

(1) Connect the harness to the junction box (Ref. AMM TASK 77-21-43-400-010).
(2) Connect the harness to the thermocouple probes (Ref. AMM TASK 77-21-15-400-010).

Subtask 77-21-43-410-051-A ** ON A/C NOT FOR ALL

B. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Remove the access platform(s).
(3) Close the thrust reverser halves (Ref. AMM TASK 78-32-00-410-010):
(a) FOR [1000EM1] (ENGINE-1), [1000EM1] (ENGINE-1)
451AL 452AR
(b) FOR [1000EM2] (ENGINE-2), [1000EM2] (ENGINE-2)
461AL 462AR.

Subtask 77-21-43-440-050-A ** ON A/C NOT FOR ALL

C. Activate the thrust reverser hydraulic control unit (Ref. AMM TASK 78-30-00-440-012).

Subtask 77-21-43-410-057-A ** ON A/C NOT FOR ALL

D. Close Access
(1) Close the fan cowls (Ref. AMM TASK 71-13-00-410-010):
(a) FOR [1000EM1] (ENGINE-1)
437AL 438AR
(b) FOR [1000EM2] (ENGINE-2)
447AL 448AR.
(2) Remove the WARNING NOTICE(S).

[Rev.10 from 2021] 2026.04.01 03:18:20 UTC