DOC AIRBUS | AMM A320FInspection/Check of the T495 Thermocouple Wiring Harness [CFMB]
TASK 77-21-10-200-002-A
Inspection/Check of the T495 Thermocouple Wiring Harness
1. Reason for the Job
This procedure gives instructions for the troubleshooting of each part and the isolation of defective subassemblies in EGT systems, because a check of the serviceability of the EGT thermocouple harness, as an assembly, is not possible. You must do this procedure step by step as described below.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment
B. Consumable Materials
C. Work Zones and Access Panels
D. Referenced Information
3. Job Set-up
Subtask 77-21-10-941-066-A ** ON A/C NOT FOR ALL
Subtask 77-21-10-280-051-A ** ON A/C NOT FOR ALL
Subtask 77-21-10-410-079-A ** ON A/C NOT FOR ALL
[Rev.10 from 2021]
2026.04.01 03:17:40 UTC
Inspection/Check of the T495 Thermocouple Wiring Harness
1. Reason for the Job
This procedure gives instructions for the troubleshooting of each part and the isolation of defective subassemblies in EGT systems, because a check of the serviceability of the EGT thermocouple harness, as an assembly, is not possible. You must do this procedure step by step as described below.
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 | 1 | ADAPTOR LEAD |
| No specific | 1 | CUP - SUCTION |
| No specific | 1 | MEGOHMMETER - 50VDC |
| No specific | AR | OHMMETER ACCURACY 0.01 OHM |
| No specific | AR | WARNING NOTICE(S) |
| No specific | Torque wrench: range to between 180 and 135 lbf.in (2.03 and 1.53 m.daN )  | |
| No specific | Torque wrench: range to between 186 and 168 lbf.in (2.10 and 1.90 m.daN ) | |
| 856A3317 | 1 | LEAD,CHECK-EGT(T495) RH WIRING HARNESS |
| 856A3318 | 2 | LEAD,CHECK-EGT(T495) LH WIRING HARNESS |
| REFERENCE | DESIGNATION |
|---|---|
| (Material No.CP8001) | lockwire 0.032 in. (0.8 mm) dia. |
| (Material No.CP8002) | lockwire 0.032 in. (0.8 mm) dia |
| 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 | |
| REFERENCE | DESIGNATION |
|---|---|
| TASK 71-13-00-010-040-B | Opening of the Fan Cowl Doors |
| TASK 71-13-00-410-040-B | Closing of the Fan Cowl Doors |
| TASK 73-21-50-210-002-A | Visual Inspection of the Wiring Harnesses |
| TASK 78-30-00-081-041-B | Make the Thrust Reverser Serviceable after Maintenance |
| TASK 78-30-00-481-041-B | Make the Thrust Reverser Unserviceable for Maintenance |
| TASK 78-36-00-010-040-B | Opening of the Thrust Reverser Doors |
| TASK 78-36-00-410-040-B | Closing of the Thrust Reverser Doors |
Wiring Diagram of the Harness of the T495 ThermocoupleSubtask 77-21-10-941-066-A ** ON A/C NOT FOR ALL
A. Safety Precautions
(1) On the center pedestal, on the ENG panel 115VU:
(a) Put a WARNING NOTICE(S) 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) to tell persons not to energize the FADEC 1(2).
Subtask 77-21-10-010-079-A ** ON A/C NOT FOR ALL (1) On the center pedestal, on the ENG panel 115VU:
(a) Put a WARNING NOTICE(S) 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) to tell persons not to energize the FADEC 1(2).
B. Get Access
(1) Open the fan cowl doors (Ref. AMM TASK 71-13-00-010-040):
(a) FOR [1000EM1] (ENGINE-1)
437AL 438AR
(b) FOR [1000EM2] (ENGINE-2)
447AL 448AR
(2) Put an ACCESS PLATFORM 1M(3 FT) in position.
Subtask 77-21-10-040-079-A ** ON A/C NOT FOR ALL Subtask 77-21-10-010-095-A ** ON A/C NOT FOR ALL (1) Open the fan cowl doors (Ref. AMM TASK 71-13-00-010-040):
(a) FOR [1000EM1] (ENGINE-1)
437AL 438AR
(b) FOR [1000EM2] (ENGINE-2)
447AL 448AR
(2) Put an ACCESS PLATFORM 1M(3 FT) in position.
D. Open the thrust reverser doors (Ref. AMM TASK 78-36-00-010-040):
(1) FOR [1000EM1] (ENGINE-1)
451AL 452AR
(2) FOR [1000EM2] (ENGINE-2)
461AL 462AR
4. Procedure(1) FOR [1000EM1] (ENGINE-1)
451AL 452AR
(2) FOR [1000EM2] (ENGINE-2)
461AL 462AR
Subtask 77-21-10-280-051-A ** ON A/C NOT FOR ALL
A. Inspection/Check of the T495 Thermocouple Wiring Harness
1 Cut and remove the lockwire.
2 Disconnect the lower extension lead from the parallel junction box of the R/H lower thermocouple lead assembly, then the branches of the main junction box assembly from the parallel boxes of L/H upper and lower thermocouple lead assemblies.
3 Connect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the parallel junction box receptacle of the thermocouple lead assembly that you have to check.
4 Connect the wires of 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the OHMMETER ACCURACY 0.01 OHM.
5 Measure and record the ohmic resistance value. Subtract the lead ohmic resistance value of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (865A3317P02) to find the ohmic resistance value A of the thermocouple lead assembly.
6 Invert the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02). Measure and record the ohmic resistance value. Subtract the lead ohmic resistance value of the tool to find the ohmic resistance value B of the thermocouple lead assembly.
7 Add the ohmic resistance values A and B, and divide them by two. The resultant value must be 0.61 ohm plus or minus 0.12 ohm.
1 Strap the two wires of the adapter lead, and connect them to a terminal of the megohmmeter.
2 Connect the other terminal of the megohmmeter to the casing. The insulation resistance value must be greater than 10 megohms.
3 Disconnect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the thermocouple lead assembly.
4 Connect the lower extension lead to the parallel junction box of the R/H lower thermocouple lead assembly, then the branches of the main junction box assembly to the parallel boxes of L/H upper and lower thermocouple lead assemblies.
5 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN ) and safety with CP8001 lockwire 0.032 in. (0.8 mm) dia. CP8002 lockwire 0.032 in. (0.8 mm) dia
1 Cut and remove the lockwire.
2 Disconnect the upper extension lead from the parallel junction box of the R/H thermocouple lead assembly (upper right T495 sector).
3 Connect the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the OHMMETER ACCURACY 0.01 OHM.
4 Measure and record the ohmic resistance value of the lead (Resistance leads).
5 Connect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the parallel junction box receptacle of the thermocouple lead assembly.
6 Connect the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the OHMMETER ACCURACY 0.01 OHM.
7 Measure and record the ohmic resistance value. Subtract the "resistance leads" value of the tool to find the ohmic resistance value A of the thermocouple lead assembly.
8 Invert the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02). Measure and record the ohmic resistance value. Subtract the "resistance leads" value of the tool to find the ohmic resistance value B of the thermocouple lead assembly.
9 Add the ohmic resistance values A and B, and divide them by two. The resultant value must be 0.64 ohm plus or minus 0.12 ohm.
1 Strap the two wires of the adapter lead, and connect them to a terminal of the megohmmeter.
2 Connect the other terminal of the megohmmeter to the casing. The insulation resistance must be greater than 10 Megohms.
3 Disconnect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the thermocouple lead assembly.
4 Connect the upper extension lead to the parallel junction box of the R/H lower thermocouple lead assembly.
5 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN ) and safety with CP8001 lockwire 0.032 in. (0.8 mm) dia. CP8002 lockwire 0.032 in. (0.8 mm) dia
1 Cut and remove the lockwires.
2 Disconnect the upper extension lead from the parallel junction box of the R/H thermocouple lead assembly (upper right T495 sector) and from the main junction box assembly receptacle.
3 Connect one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to each upper extension lead connector.
4 Connect the wires of one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to the ohmmeter, and short the wires of the second one.
5 Measure the ohmic resistance value. Subtract the two ohmic lead resistance values of the tool to find the ohmic resistance value of the upper extension lead.
6 The final resistance value must be 1.38 ohm plus or minus 0.18 ohm.
(b) Do an insulation check as follows:
2 The insulation resistance value between the two conductors must be greater than 10 Megohms.
3 The insulation resistance value between each conductor and the connector casing must be greater than 10 Megohms.
4 Disconnect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the upper extension lead connector.
5 Connect the upper extension lead to the parallel junction box of the R/H thermocouple lead assembly (upper right T495 sector) and to the main junction box assembly receptacle.
6 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN ) and safety with CP8001 lockwire 0.032 in. (0.8 mm) dia. CP8002 lockwire 0.032 in. (0.8 mm) dia
1 Cut and remove the lockwires.
2 Disconnect the lower extension lead from the parallel junction box of the R/H lower thermocouple lead assembly (lower right T495 sector) and from the main junction box assembly receptacle.
3 Connect one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to each lower extension lead connector.
4 Connect the wires of one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to an ohmmeter, and short the wires of the second one.
5 Measure the ohmic resistance value. Subtract the two ohmic lead resistance values of the tool to find the ohmic resistance value of the lower extension lead.
6 The final resistance value must be 1.60 ohm plus or minus 0.18 ohm.
(b) Do an insulation check as follows:
2 The insulation resistance value between the two conductors must be greater than 10 Megohms.
3 The insulation resistance value between each conductor and the connector casing must be greater than 10 Megohms.
4 Disconnect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the lower extension lead connector.
5 Connect the lower extension lead to the parallel junction box of the R/H lower thermocouple lead assembly (lower right T495 sector) and to the main junction box assembly receptacle.
6 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN ) and safety with CP8001 lockwire 0.032 in. (0.8 mm) dia. CP8002 lockwire 0.032 in. (0.8 mm) dia
1 Cut and remove the lockwires.
2 Disconnect the CJ13 harness and the upper and lower extension leads from the main junction box receptacles.
3 Cut and remove the lockwires.
4 Disconnect the branch connectors of main junction box assembly from the parallel junction box receptacles of L/H upper and lower thermocouple lead assemblies.
5 Connect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to one of the two branch connectors.
6 Short the wires of 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02).
7 Connect the ADAPTOR LEAD connector MIL-C 5015-10SL3S with test lead to the CJ13 interface harness receptacle.
9 Measure the ohmic resistance value.
10 Subtract the ohmic resistance values of the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) and of the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the value given in paragraph above.
11 The final resistance value must be 2.43 ohm plus or minus 0.23 ohm.
13 Repeat the same electrical check.
14 Disconnect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the branch connector.
(b) Do a resistance check of the wires inside the main junction box assembly as follows:
1 Connect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the main junction box receptacle which receives the lower extension lead connector.
2 Short the wires of 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02).
3 Measure the ohmic resistance value on the OHMMETER ACCURACY 0.01 OHM, still connected to the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S).
4 Subtract the ohmic resistance values of the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) and of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the value given in paragraph above.
5 The final resistance value must be 0.843 ohm plus or minus 0.14 ohm.
7 Measure the ohmic resistance value on the OHMMETER ACCURACY 0.01 OHM still connected to the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S).
8 Subtract the ohmic resistance values of the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) and of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the value given in paragraph above.
9 The final resistance value must be 0.07 ohm plus or minus 0.05 ohm.
(c) Do an insulation resistance check as follows:
1 Connect a megohmmeter to the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S).
2 The insulation resistance between the two conductors connected to pins A and B of the CJ13 harness interface receptacle must be greater than 10 Megohms.
3 The insulation resistance between each conductor and connector casing or receptacle casing must be greater than 10 Megohms.
4 Disconnect the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) from the main junction box assembly receptacle.
5 Connect the CJ13 harness to the main junction box assembly receptacle.
6 Torque the CJ13 harness to between 180 and 135 lbf.in (2.03 and 1.53 m.daN ) and safety with CP8001 lockwire 0.032 in. (0.8 mm) dia. CP8002 lockwire 0.032 in. (0.8 mm) dia
7 Connect the upper and lower extension lead connectors to the main junction box assembly receptacles.
8 Connect the branch connectors of main junction box assembly to the parallel junction box receptacles of L/H upper and lower thermocouple lead assemblies.
9 Torque the 4 connecting nuts to between 186 and 168 lbf.in (2.10 and 1.90 m.daN ) and safety with CP8001 lockwire 0.032 in. (0.8 mm) dia. CP8002 lockwire 0.032 in. (0.8 mm) dia
5. Close-upCAUTION:
DO THE ELECTRICAL INSPECTION/CHECK OF THE T495 THERMOCOUPLE WIRING HARNESS AT AMBIENT TEMPERATURE.
CAUTION:
REMOVE THE NEAREST CLAMPS WHICH ATTACH THE LEADS TO THE BRACKETS, BEFORE YOU DISCONNECT THE CONNECTORS.
(1) Electrical check of the L/H lower and upper thermocouple (2 probes) lead assemblies and R/H lower thermocouple (2 probes) lead assembly. NOTE: Make sure that the connectors are clean and clear of unwanted materials. If necessary, clean the connectors (Ref. AMM TASK 73-21-50-210-002).
(a) Do a resistance check as follows: 1 Cut and remove the lockwire.
2 Disconnect the lower extension lead from the parallel junction box of the R/H lower thermocouple lead assembly, then the branches of the main junction box assembly from the parallel boxes of L/H upper and lower thermocouple lead assemblies.
3 Connect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the parallel junction box receptacle of the thermocouple lead assembly that you have to check.
4 Connect the wires of 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the OHMMETER ACCURACY 0.01 OHM.
5 Measure and record the ohmic resistance value. Subtract the lead ohmic resistance value of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (865A3317P02) to find the ohmic resistance value A of the thermocouple lead assembly.
6 Invert the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02). Measure and record the ohmic resistance value. Subtract the lead ohmic resistance value of the tool to find the ohmic resistance value B of the thermocouple lead assembly.
7 Add the ohmic resistance values A and B, and divide them by two. The resultant value must be 0.61 ohm plus or minus 0.12 ohm.
NOTE: Resistance values increase 10 percent higher at 176 deg.F (80.00 deg.C).
(b) Do an insulation check as follows: 1 Strap the two wires of the adapter lead, and connect them to a terminal of the megohmmeter.
2 Connect the other terminal of the megohmmeter to the casing. The insulation resistance value must be greater than 10 megohms.
3 Disconnect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the thermocouple lead assembly.
4 Connect the lower extension lead to the parallel junction box of the R/H lower thermocouple lead assembly, then the branches of the main junction box assembly to the parallel boxes of L/H upper and lower thermocouple lead assemblies.
5 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN )
and safety with CAUTION:
REMOVE THE NEAREST CLAMPS WHICH ATTACH THE LEADS TO THE BRACKETS, BEFORE YOU DISCONNECT THE CONNECTORS.
(2) Electrical check of the R/H thermocouple (3 probes) lead assembly. NOTE: Make sure that the connectors are clean and clear of unwanted materials. If necessary, clean the connectors (Ref. AMM TASK 73-21-50-210-002).
(a) Do a resistance check as follows: 1 Cut and remove the lockwire.
2 Disconnect the upper extension lead from the parallel junction box of the R/H thermocouple lead assembly (upper right T495 sector).
3 Connect the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the OHMMETER ACCURACY 0.01 OHM.
4 Measure and record the ohmic resistance value of the lead (Resistance leads).
5 Connect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the parallel junction box receptacle of the thermocouple lead assembly.
6 Connect the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the OHMMETER ACCURACY 0.01 OHM.
7 Measure and record the ohmic resistance value. Subtract the "resistance leads" value of the tool to find the ohmic resistance value A of the thermocouple lead assembly.
8 Invert the wires of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02). Measure and record the ohmic resistance value. Subtract the "resistance leads" value of the tool to find the ohmic resistance value B of the thermocouple lead assembly.
9 Add the ohmic resistance values A and B, and divide them by two. The resultant value must be 0.64 ohm plus or minus 0.12 ohm.
NOTE: Resistance values increase 10 percent higher at 176 deg.F (80.00 deg.C).
(b) Do an insulation check as follows: 1 Strap the two wires of the adapter lead, and connect them to a terminal of the megohmmeter.
2 Connect the other terminal of the megohmmeter to the casing. The insulation resistance must be greater than 10 Megohms.
3 Disconnect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the thermocouple lead assembly.
4 Connect the upper extension lead to the parallel junction box of the R/H lower thermocouple lead assembly.
5 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN )
and safety with CAUTION:
REMOVE THE NEAREST CLAMPS WHICH ATTACH THE LEADS TO THE BRACKETS, BEFORE YOU DISCONNECT THE CONNECTORS.
(3) Electrical check of the upper extension lead assembly. NOTE: Make sure that the connectors are clean and clear of unwanted materials. If necessary, clean the connectors (Ref. AMM TASK 73-21-50-210-002).
(a) Do a resistance check as follows: 1 Cut and remove the lockwires.
2 Disconnect the upper extension lead from the parallel junction box of the R/H thermocouple lead assembly (upper right T495 sector) and from the main junction box assembly receptacle.
3 Connect one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to each upper extension lead connector.
4 Connect the wires of one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to the ohmmeter, and short the wires of the second one.
5 Measure the ohmic resistance value. Subtract the two ohmic lead resistance values of the tool to find the ohmic resistance value of the upper extension lead.
6 The final resistance value must be 1.38 ohm plus or minus 0.18 ohm.
NOTE: Resistance values increase 10 percent higher at 176 deg.F (80.00 deg.C).
7 Disconnect the shorted 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02). (b) Do an insulation check as follows:
CAUTION:
DISCONNECT THE SHORTED ADAPTER LEAD.
1 Connect the MEGOHMMETER - 50VDC to the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) still connected. 2 The insulation resistance value between the two conductors must be greater than 10 Megohms.
3 The insulation resistance value between each conductor and the connector casing must be greater than 10 Megohms.
4 Disconnect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the upper extension lead connector.
5 Connect the upper extension lead to the parallel junction box of the R/H thermocouple lead assembly (upper right T495 sector) and to the main junction box assembly receptacle.
6 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN )
and safety with CAUTION:
REMOVE THE NEAREST CLAMPS WHICH ATTACH THE LEADS TO THE BRACKETS, BEFORE YOU DISCONNECT THE CONNECTORS.
(4) Electrical check of the lower extension lead assembly. NOTE: Make sure that the connectors are clean and clear of unwanted materials. If necessary, clean the connectors (Ref. AMM TASK 73-21-50-210-002).
(a) Do a resistance check as follows: 1 Cut and remove the lockwires.
2 Disconnect the lower extension lead from the parallel junction box of the R/H lower thermocouple lead assembly (lower right T495 sector) and from the main junction box assembly receptacle.
3 Connect one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to each lower extension lead connector.
4 Connect the wires of one 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to an ohmmeter, and short the wires of the second one.
5 Measure the ohmic resistance value. Subtract the two ohmic lead resistance values of the tool to find the ohmic resistance value of the lower extension lead.
6 The final resistance value must be 1.60 ohm plus or minus 0.18 ohm.
NOTE: Resistance values increase 10 percent higher at 176 deg.F (80.00 deg.C).
7 Disconnect the shorted 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02). (b) Do an insulation check as follows:
CAUTION:
DISCONNECT THE SHORTED CHECK - LEAD FOR WIRING HARNESS EGT (856A3318P02).
1 Connect a CUP - SUCTION to the adapter lead 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) still connected. 2 The insulation resistance value between the two conductors must be greater than 10 Megohms.
3 The insulation resistance value between each conductor and the connector casing must be greater than 10 Megohms.
4 Disconnect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the lower extension lead connector.
5 Connect the lower extension lead to the parallel junction box of the R/H lower thermocouple lead assembly (lower right T495 sector) and to the main junction box assembly receptacle.
6 Torque the connecting nut to between 186 and 168 lbf.in (2.10 and 1.90 m.daN )
and safety with CAUTION:
REMOVE THE NEAREST CLAMPS WHICH ATTACH THE LEADS TO THE BRACKETS, BEFORE YOU DISCONNECT THE CONNECTORS.
(5) Electrical checks of the main junction box assembly. NOTE: Make sure that the connectors are clean and clear of unwanted materials. If necessary, clean the connectors (Ref. AMM TASK 73-21-50-210-002).
(a) Do a resistance check as follows: 1 Cut and remove the lockwires.
2 Disconnect the CJ13 harness and the upper and lower extension leads from the main junction box receptacles.
3 Cut and remove the lockwires.
4 Disconnect the branch connectors of main junction box assembly from the parallel junction box receptacles of L/H upper and lower thermocouple lead assemblies.
5 Connect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) to one of the two branch connectors.
6 Short the wires of 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02).
7 Connect the ADAPTOR LEAD connector MIL-C 5015-10SL3S with test lead to the CJ13 interface harness receptacle.
NOTE: The ADAPTOR LEAD connector MIL-C 5015-10SL3S can be locally manufactured following its reference.
8 Connect the wires of the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) to the OHMMETER ACCURACY 0.01 OHM. 9 Measure the ohmic resistance value.
10 Subtract the ohmic resistance values of the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) and of the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the value given in paragraph above.
11 The final resistance value must be 2.43 ohm plus or minus 0.23 ohm.
NOTE: Resistance values increase 10 percent higher at 176 deg.F (80.00 deg.C).
12 Disconnect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02), shorted from the branch connector, and connect it to the other branch connector of main junction box assembly. 13 Repeat the same electrical check.
14 Disconnect the 856A3318 LEAD,CHECK-EGT(T495) LH WIRING HARNESS (856A3318P02) from the branch connector.
(b) Do a resistance check of the wires inside the main junction box assembly as follows:
1 Connect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) to the main junction box receptacle which receives the lower extension lead connector.
2 Short the wires of 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02).
3 Measure the ohmic resistance value on the OHMMETER ACCURACY 0.01 OHM, still connected to the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S).
4 Subtract the ohmic resistance values of the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) and of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the value given in paragraph above.
5 The final resistance value must be 0.843 ohm plus or minus 0.14 ohm.
NOTE: Resistance values increase 10 percent higher at 176 deg.F (80.00 deg.C).
6 Disconnect the shorted 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the main junction box receptacle and connect it to the main junction box receptacle which receives the upper extension lead connector. 7 Measure the ohmic resistance value on the OHMMETER ACCURACY 0.01 OHM still connected to the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S).
8 Subtract the ohmic resistance values of the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) and of the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02) from the value given in paragraph above.
9 The final resistance value must be 0.07 ohm plus or minus 0.05 ohm.
NOTE: Resistance values increase 10 percent higher at 176 deg.F (80.00 deg.C).
10 Disconnect the 856A3317 LEAD,CHECK-EGT(T495) RH WIRING HARNESS (856A3317P02). (c) Do an insulation resistance check as follows:
1 Connect a megohmmeter to the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S).
2 The insulation resistance between the two conductors connected to pins A and B of the CJ13 harness interface receptacle must be greater than 10 Megohms.
3 The insulation resistance between each conductor and connector casing or receptacle casing must be greater than 10 Megohms.
4 Disconnect the ADAPTOR LEAD connector with test lead (MIL-C 5015-10SL3S) from the main junction box assembly receptacle.
5 Connect the CJ13 harness to the main junction box assembly receptacle.
6 Torque the CJ13 harness to between 180 and 135 lbf.in (2.03 and 1.53 m.daN )
and safety with 7 Connect the upper and lower extension lead connectors to the main junction box assembly receptacles.
8 Connect the branch connectors of main junction box assembly to the parallel junction box receptacles of L/H upper and lower thermocouple lead assemblies.
9 Torque the 4 connecting nuts to between 186 and 168 lbf.in (2.10 and 1.90 m.daN )
and safety with Subtask 77-21-10-410-079-A ** ON A/C NOT FOR ALL
A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the thrust reverser doors (Ref. AMM TASK 78-36-00-410-040):
(a) FOR [1000EM1] (ENGINE-1)
451AL 452AR
(b) FOR [1000EM2] (ENGINE-2)
461AL 462AR
Subtask 77-21-10-440-065-A ** ON A/C NOT FOR ALL Subtask 77-21-10-410-081-A ** ON A/C NOT FOR ALL (1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the thrust reverser doors (Ref. AMM TASK 78-36-00-410-040):
(a) FOR [1000EM1] (ENGINE-1)
451AL 452AR
(b) FOR [1000EM2] (ENGINE-2)
461AL 462AR