DOC AIRBUS | TSM A320FComponent and Harness Intermittent Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults
TASK 71-00-00-810-835-A
Component and Harness Intermittent Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults
1. Possible Causes
2. Job Set-up Information
A. Referenced Information
3. Fault Confirmation
Subtask 71-00-00-710-100-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:40:00 UTC
Component and Harness Intermittent Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults
1. Possible Causes
2. Job Set-up Information
A. Referenced Information
| REFERENCE | DESIGNATION |
|---|---|
| TSM TASK 71-00-00-810-834-A | General Troubleshooting Guidelines for Additional Troubleshooting Information |
| AMM 70-70-00-910-801 | SPOP 430 - Application of Electrical Contact Enhancer for Wiring Harnesses |
| AMM 70-70-00-910-803 | SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses |
| AMM 71-00-00-710-805 | Test No. 4 - Power Acceleration/Deceleration Test |
| AMM 73-21-00-710-807 | Test No.6 - EEC Operation Test (Idle Test) |
| AMM 73-21-00-710-809 | Test No.15 - Operation Test (Dry Motor) of the FADEC System Engine Actuators |
| AMM 73-21-00-710-810 | FADEC System Wiring Harness Operation Test |
Subtask 71-00-00-710-100-A ** ON A/C NOT FOR ALL
A. Not Applicable
4. Fault Isolation- This procedure will help to isolate any intermittent maintenance messages caused by a problem in the component or wiring.
WARNING:
BE CAREFUL WHEN YOU DO WORK ON THE ENGINE AFTER SHUTDOWN. THE ENGINE CAN STAY HOT FOR A LONG TIME. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.
WARNING:
REFER TO THE MSDS FOR ALL MATERIAL USED AND THE MANUFACTURER'S SAFETY INSTRUCTIONS FOR ALL EQUIPMENT USED. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.
CAUTION:
MAKE SURE YOU REMOVE ELECTRICAL POWER FROM THE EEC BEFORE YOU REMOVE THE ELECTRICAL CONNECTORS. IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE EEC CAN OCCUR.
Subtask 71-00-00-810-108-A ** ON A/C NOT FOR ALL A. Component and Harness Intermittent Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults
(1) Read the general troubleshooting guidelines for additional troubleshooting information before you perform the task (Ref. TSM TASK 71-00-00-810-834).
(2) Use the component locator graphics and the wiring diagrams that are referenced in the troubleshooting procedure for the fault that you are trying to fix.
(3) Intermittent feedback type (wraparound, range/rate, disagree) maintenance messages:
(a) Feedback-type maintenance messages that will not usually repeat when the FADEC is interrogated following normal shutdown. This type of fault is usually caused by a problem within a wiring harness or connector during flight or ground phases when the engine is running. Troubleshooting should be performed for an intermittent fault that occurs more than two times.
2 Find all the connectors and wiring harness segments in the circuit that you want to test from the Electronic Engine Control (EEC) to the component. Use the component locator and wiring schematic in the applicable troubleshooting procedure to help you find the connectors. The Aircraft Wiring Manual (AWM) and the Aircraft Schematics Manual (ASM) can also be used to provide additional information.
3 Examine the wiring harness, electrical connectors and backshells for possible problems between the EEC and the component:
a Look for wiring harness damage.
b Look for loose or damaged electrical connectors.
c Look for loose or damaged backshells.
d Do a check of the mating connector for alignment and damage. Look for contacts pushed rearward toward the connector face. If you find a pin with one bend that is less than 20 degrees, it can be straightened. You can straighten the bent pin by using a spare mating socket as a tool.
e Do a check of the connectors for fretting or contamination. If fretting or contamination is found, clean the contacts with contact cleaner AMM 70-70-00-910-803.
f Replace the wiring harness as necessary.
4 Do a check of the mating sockets and pins and make sure that each connector has a good interference fit as follows:
a Make a test lead approximately 6 in. (152.40 mm) long with a socket at one end and the same size (gage) pin at the other. Make sure that you use the correct size for the pin or socket to be tested. Damage to the connector will result if you test a socket with a pin that is too large. To achieve the best results, use a new test lead for each electrical connector.
b To test the sockets, insert the pin from the test lead into each socket of the connector in the suspect circuit. Make sure that there is some resistance or friction felt when you install and remove the pin from the test lead from each socket.
c To test the pins, insert the pin from the connector of the suspect circuit into the socket on the test lead. Make sure that there is some resistance or friction felt when you install and remove the socket from the test lead from each pin.
d Repeat the steps with the remaining connector contacts between the EEC and the component as necessary. If the test finds that there is a loose interference fit, this can be the cause of the intermittent fault. The wiring harness or component that has a connector with a loose interference fit condition should be replaced.
e A temporary repair for contacts with a loose interference fit can be done by using an electrical contact enhancer per SPOP 430 AMM 70-70-00-910-801.
5 If the intermittent fault continues, do the steps that follow:
a Replace the applicable component.
b Replace the applicable wiring harness.
c Replace the EEC.
6 To correct a maintenance message, one or more engine wiring harnesses may need to be removed or replaced. If a wiring harness that is replaced affects another system that requires an engine run at idle to confirm the fault, do an engine run at idle AMM 73-21-00-710-807 and make sure that no additional engine system faults have been set.
7 In some cases, an engine run at idle or higher power setting or a subsequent flight may be necessary to confirm that the troubleshooting steps which were performed have fixed the problem.
(b) Intermittent out-of-position type maintenance messages can be caused by a sticking external linkage or sticking actuator. They can also be caused by a reduction in servo pressure or wiring problems. Do the troubleshooting steps for these maintenance messages as described in the specific fault isolation procedures. Troubleshooting should be performed for an intermittent fault that occurs more than two times.
1 The Multipurpose Control & Display Unit (MCDU) on the flight deck can be used to perform an interactive engine systems test to help with troubleshooting. The test can also be used for repair confirmation as applicable. The test is as follows:
a Operational test of the engine actuators AMM 73-21-00-710-809.
2 Do a repair confirmation before you return the engine to service. This step should be performed to make sure that you have corrected the problem. An engine run at idle AMM 73-21-00-710-807, an engine run at high power AMM 71-00-00-710-805 or a subsequent flight may be necessary to confirm that the troubleshooting steps which were performed have fixed the problem.
3 To correct a maintenance message, one or more engine wiring harnesses may need to be removed or replaced. If a wiring harness that is replaced affects another system that requires an engine run to confirm the fault, do an engine run at idle AMM 73-21-00-710-807 and make sure that no additional engine system faults have been set.
4 If the intermittent fault continues, do the steps that follow:
a Replace the component.
b Replace the applicable wiring harness.
c Replace the EEC.
(1) Read the general troubleshooting guidelines for additional troubleshooting information before you perform the task (Ref. TSM TASK 71-00-00-810-834).
(2) Use the component locator graphics and the wiring diagrams that are referenced in the troubleshooting procedure for the fault that you are trying to fix.
(3) Intermittent feedback type (wraparound, range/rate, disagree) maintenance messages:
(a) Feedback-type maintenance messages that will not usually repeat when the FADEC is interrogated following normal shutdown. This type of fault is usually caused by a problem within a wiring harness or connector during flight or ground phases when the engine is running. Troubleshooting should be performed for an intermittent fault that occurs more than two times.
NOTE: Class 1 and 2 maintenance messages are recorded on the Post Flight Report (PFR) at the first engine start + 30 seconds. Look at the ground report to make sure that you gather all the information for the fault.
1 Do the ground harness test AMM 73-21-00-710-810. 2 Find all the connectors and wiring harness segments in the circuit that you want to test from the Electronic Engine Control (EEC) to the component. Use the component locator and wiring schematic in the applicable troubleshooting procedure to help you find the connectors. The Aircraft Wiring Manual (AWM) and the Aircraft Schematics Manual (ASM) can also be used to provide additional information.
3 Examine the wiring harness, electrical connectors and backshells for possible problems between the EEC and the component:
a Look for wiring harness damage.
b Look for loose or damaged electrical connectors.
c Look for loose or damaged backshells.
d Do a check of the mating connector for alignment and damage. Look for contacts pushed rearward toward the connector face. If you find a pin with one bend that is less than 20 degrees, it can be straightened. You can straighten the bent pin by using a spare mating socket as a tool.
e Do a check of the connectors for fretting or contamination. If fretting or contamination is found, clean the contacts with contact cleaner AMM 70-70-00-910-803.
f Replace the wiring harness as necessary.
4 Do a check of the mating sockets and pins and make sure that each connector has a good interference fit as follows:
a Make a test lead approximately 6 in. (152.40 mm) long with a socket at one end and the same size (gage) pin at the other. Make sure that you use the correct size for the pin or socket to be tested. Damage to the connector will result if you test a socket with a pin that is too large. To achieve the best results, use a new test lead for each electrical connector.
b To test the sockets, insert the pin from the test lead into each socket of the connector in the suspect circuit. Make sure that there is some resistance or friction felt when you install and remove the pin from the test lead from each socket.
c To test the pins, insert the pin from the connector of the suspect circuit into the socket on the test lead. Make sure that there is some resistance or friction felt when you install and remove the socket from the test lead from each pin.
d Repeat the steps with the remaining connector contacts between the EEC and the component as necessary. If the test finds that there is a loose interference fit, this can be the cause of the intermittent fault. The wiring harness or component that has a connector with a loose interference fit condition should be replaced.
e A temporary repair for contacts with a loose interference fit can be done by using an electrical contact enhancer per SPOP 430 AMM 70-70-00-910-801.
5 If the intermittent fault continues, do the steps that follow:
a Replace the applicable component.
b Replace the applicable wiring harness.
c Replace the EEC.
6 To correct a maintenance message, one or more engine wiring harnesses may need to be removed or replaced. If a wiring harness that is replaced affects another system that requires an engine run at idle to confirm the fault, do an engine run at idle AMM 73-21-00-710-807 and make sure that no additional engine system faults have been set.
7 In some cases, an engine run at idle or higher power setting or a subsequent flight may be necessary to confirm that the troubleshooting steps which were performed have fixed the problem.
(b) Intermittent out-of-position type maintenance messages can be caused by a sticking external linkage or sticking actuator. They can also be caused by a reduction in servo pressure or wiring problems. Do the troubleshooting steps for these maintenance messages as described in the specific fault isolation procedures. Troubleshooting should be performed for an intermittent fault that occurs more than two times.
1 The Multipurpose Control & Display Unit (MCDU) on the flight deck can be used to perform an interactive engine systems test to help with troubleshooting. The test can also be used for repair confirmation as applicable. The test is as follows:
a Operational test of the engine actuators AMM 73-21-00-710-809.
2 Do a repair confirmation before you return the engine to service. This step should be performed to make sure that you have corrected the problem. An engine run at idle AMM 73-21-00-710-807, an engine run at high power AMM 71-00-00-710-805 or a subsequent flight may be necessary to confirm that the troubleshooting steps which were performed have fixed the problem.
3 To correct a maintenance message, one or more engine wiring harnesses may need to be removed or replaced. If a wiring harness that is replaced affects another system that requires an engine run to confirm the fault, do an engine run at idle AMM 73-21-00-710-807 and make sure that no additional engine system faults have been set.
4 If the intermittent fault continues, do the steps that follow:
a Replace the component.
b Replace the applicable wiring harness.
c Replace the EEC.