DOC AIRBUS | TSM A320FFailure of the FMU Overspeed Valve on Engine 2
1. Possible Causes
NOTE: This task is to troubleshoot the Clear Language Message (CLM) FMU/HC/EEC2. The fault acronyms listed
in the fault confirmation section below will help you focus on the correct cause of this CLM.
· FMU ( 4000KC )
· EEC ( 4000KS )
2 Job Set-up Information
A. Referenced Information
REFERENCE DESIGNATION
Ref. AMM 24-41-00-861-002 Energize the Aircraft Electrical Circuits from the External Power
Ref. AMM 24-41-00-862-002 De-energize the Aircraft Electrical Circuits Supplied from the External
Power
Ref. AMM 31-60-00-860-002 EIS Stop Procedure
Ref. AMM 70-23-15-912-010 Connection of Electrical Connectors
Ref. AMM 71-00-00-710-018 Discontinued Start, Restart and Shutdown Procedures
Ref. AMM 71-00-00-710-043 Normal Engine Automatic Start Procedure
Ref. AMM 71-00-00-710-047 Normal Engine Manual Start Procedure
Ref. AMM 71-50-00-210-010 Wire Harness Visual Inspection - All Power Plant Electrical Cables
Ref. AMM 73-22-00-710-040 Operational Test of the FADEC SYSTEM on the Ground
Ref. AMM 73-22-34-000-010 Removal of the Electronic Engine Control (EEC)
Ref. AMM 73-22-34-400-010 Installation of the Electronic Engine Control (EEC)
Ref. AMM 73-22-52-000-010 Removal of the Fuel Metering Unit (FMU)
Ref. AMM 73-22-52-400-010 Installation of the Fuel Metering Unit (FMU)
Ref. ASM 73-25-18
70-00-00-03-13 STANDARD PRACTICES - ENGINE - GENERAL - TASK SUPPORTING
DATA
FMU Overspeed Valve SHEET 1
Figure 73(IAE)-22-00-991-00200-B / SHEET 1/1 - FMU Overspeed Valve not printed, as per printing
preferences
3. Fault Confirmation
Subtask 73-22-00-860-066-A
A. Job Set-up
(1) Energize the aircraft electrical circuits
Ref. AMM 24-41-00-861-002 .
(2) On the overhead panel 50VU, put the ENG FADEC GND PWR 2 pushbutton switches in the ON
position.
Subtask 73-22-00-710-092-B
B. Identify the test to make sure that the fault is present.
NOTE: Troubleshooting can start immediately without doing the fault confirmation if this CLM was indicated
in multiple flight or ground legs.
(1) Do the CFDS message decoding to identify the fault code related to the CLM
(Ref. TSM 70-00-00-03) .
(2) If the readout gives the fault acronym OSWAF in FADEC 2A or FADEC 2B, do the FADEC system
operational test for fault confirmation Ref. AMM 73-22-00-710-040 .
(3) If the readout gives the fault acronyms OSRLF, OSFLOP or OSFLCL in FADEC 2A or FADEC 2B, do
the steps in Para. 3.C. for fault confirmation.
Subtask 73-22-00-710-253-B
C. Test for Fault Acronyms OSRLF, OSFLOP and OSFLCL
(1) On the overhead panel 50VU, put the ENG FADEC GND PWR 2 pushbutton switch in the ON
position.
NOTE: This action resets the FADEC memory.
(2) Push the INIT mode key. The INIT page comes into view.
(3) Start the engine 2 by the normal engine automatic start procedure Ref. AMM 71-00-00-710-043 or
the normal engine manual start procedure Ref. AMM 71-00-00-710-047 .
NOTE: You must operate the engine 2 for at least 3 minutes. If not, the LAST LEG REPORT will not
be erased and the fault will not be kept again in the EEC LAST LEG DEPORT.
(4) Do the shutdown of the engine 2 by discontinued start, restart and shutdown procedure Ref.
AMM 71-00-00-710-018 .
(5) Read the LAST LEG REPORT and the scheduled maintenance report of the FADEC (2A and 2B)
menu on the MCDU (Ref. TSM 70-00-00-03) .
(a) Make a record of the fault message.
(b) Make a record of the channel FADEC 2A or FADEC 2B which found the fault.
(c) Do the CFDS message decoding and read the flight data and ground data to identify the fault
code.
4. Fault Isolation
(Ref. Fig. FMU Overspeed Valve SHEET 1)
Subtask 73-22-00-810-071-B
A. Fault Isolation for Fault Acronym OSWAF
A torque motor Wrap Around Fault (WAF) was found in channel A or B. The circuit for the overspeed valve
is open, short to ground, or has a wire-to-wire short.
NOTE: At any time during this procedure, you can do the steps in Para 3 to make sure that the fault is corrected.
NOTE: the removal and installation of the electrical connectors can correct this fault.
(1) If the fault was found in channel A, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J5) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 :
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-B) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel A torque motor circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts J and H are not shorted to ground.
2 Make sure that contacts J and H are not shorted to any other contact in the connector.
3 Make sure that resistance from contact J to contact H is between 43 and 110 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J5) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the torque motor wiring in the channel A harness. Look for:
1 Wire-to-wire shorts and shorts to ground
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Torque Motor Circuit Channel A Harness
FMU (4000KC) EEC (4000KS)
4000KC-B 4000KS-J5
Contacts Contacts
J J
H d
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for the fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSWAF, return the engine to service.
2 If the test gives the fault acronym OSWAF, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If this fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 Ref. AMM 73-22-34-400-010 .
(2) If the fault was found in channel B, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J11) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 :
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-C) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel B torque motor circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts J and H are not shorted to ground.
2 Make sure that contacts J and H are not shorted to any other contacts in the connector.
3 Make sure that the resistance from contact J to contact H is between 43 and 110 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J11) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the torque motor wiring in the channel B harness. Look for:
1 Wire-to-wire shorts and shorts to ground
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Torque Motor Circuit Channel B Harness
FMU (4000KC) EEC (4000KS)
4000KC-C 4000KS-J11
Contacts Contacts
J J
H d
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for the fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSWAF, return the engine to service.
2 If the test gives the fault acronym OSWAF, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If the fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
Subtask 73-22-00-810-181-B
B. Fault Isolation for Fault Acronym OSRLF
An overspeed overcurrent sense fault was found in channel A or B.
NOTE: At any time during this procedure, you can do the steps in Para 3 to make sure that the fault is corrected.
NOTE: Removal and installation of the electrical connectors can correct this fault.
(1) If the fault was found in channel A, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J5) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 .
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-B) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel A torque motor circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts J and H are not shorted to ground.
2 Make sure that contacts J and H are not shorted to any other contacts in the connector.
3 Make sure the resistance from contact J to contact H is between 43 and 110 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J5) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the torque motor wiring in the channel A harness. Look for:
1 Wire-to-wire shorts and shorts to ground
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Torque Motor Circuit Channel A Harness
FMU (4000KC) EEC (4000KS)
4000KC-B 4000KS-J5
Contacts Contacts
J J
H d
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for the fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSRLF, return the engine to service.
2 If the test gives the fault acronym OSRLF, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If the fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
(2) If the fault was found in channel B, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J11) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 :
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-C) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel B torque motor circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts J and H are not shorted to ground.
2 Make sure that contacts J and H are not shorted to any other contacts in the connector.
3 Make sure that the resistance from contact J to contact H is between 43 and 110 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J11) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the torque motor wiring in the Channel B harness. Look for:
1 Wire-to-wire shorts and shorts to ground
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity.
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Torque Motor Circuit Channel B Harness
FMU (4000KC) EEC (4000KS)
4000KC-C 4000KS-J11
Contacts Contacts
J J
H d
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for this fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSRLF, return the engine to service.
2 If the test gives the fault acronym OSRLF, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If the fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
Subtask 73-22-00-810-184-A
C. Fault Isolation for Fault Acronym OSFLOP
An overspeed valve fault was found in channel A or B. The circuit for the overspeed valve is in the open
position due to a short to ground, or has a wire-to-wire short.
NOTE: At any time during this procedure, you can do the steps in Para 3 to make sure that the fault is corrected.
NOTE: Removal and installation of the electrical connectors can correct this fault.
(1) If the fault was found in channel A, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J2) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 .
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-B) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel A switch circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts L and K are not shorted to ground.
2 Make sure that contacts L and K are not shorted to any other contacts in the connector.
3 Make sure that the resistance from contact L to contact K is between 0 and 10 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J2) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the switch wiring in the channel A harness. Look for:
1 Wire-to-wire shorts and shorts to ground.
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Valve Switch Circuit Channel A Harness
FMU (4000KC) EEC (4000KS)
4000KC-B 4000KS-J2
Contacts Contacts
L Y
K Z
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for the fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSFLOP, return the engine to service.
2 If the test gives the fault acronym OSFLOP, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If the fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
(2) If the fault was found in channel B, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J8) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 :
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-C) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel B switch circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts L and K are not shorted to ground.
2 Make sure that contacts L and K are not shorted to any other contacts in the connector.
3 Make sure that the resistance from contact L to contact K is between 0 and 10 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J8) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the torque motor wiring in the channel B harness. Look for:
1 Wire-to-wire shorts and shorts to ground
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Valve Switch Circuit Channel B Harness
FMU (4000KC) EEC (4000KS)
4000KC-C 4000KS-J8
Contacts Contacts
L Y
K Z
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for the fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSFLOP, return the engine to service.
2 If the test gives the fault acronym OSFLOP, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If this fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
Subtask 73-22-00-810-185-A
D. Fault Isolation for Fault Acronym OSFLCL
An overspeed valve fault was found in channel A or B. The circuit for the overspeed valve is in the open
position due to a short to ground, or has a wire-to-wire short.
NOTE: At any time during this procedure, you can do the steps in Para 3 to make sure that the fault is corrected.
NOTE: the removal and installation of the electrical connectors can correct this fault.
(1) If the fault was found in channel A, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J2) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 .
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-B) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel A switch circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts L and K are not shorted to ground.
2 Make sure that contacts L and K are not shorted to any other contacts in the connector.
3 Make sure that the resistance from contact L to contact K is between 0 and 10 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J2) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the switch wiring in the channel A harness. Look for:
1 Wire-to-wire shorts and shorts to ground
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between the wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Valve Switch Circuit Channel A Harness
FMU (4000KC) EEC (4000KS)
4000KC-B 4000KS-J2
Overspeed Valve Switch Circuit Channel A Harness
FMU (4000KC) EEC (4000KS)
Contacts Contacts
L Y
K Z
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for the fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSFLCL, return the engine to service.
2 If the test gives the fault acronym OSFLCL, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If this fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
(2) If the fault was found in channel B, do the following steps:
(a) Visually examine the harness from the EEC connector (4000KS-J8) to the FMU (4000KC) Ref.
AMM 71-50-00-210-010 :
1 Look for harness damage.
2 Look for loose or damaged connectors.
3 Look for loose or damaged backshells.
NOTE: Loose backshells must be disassembled and examined for internal wire chafing.
4 If a problem exists with the harness, repair or replace as necessary.
(b) If no problems are found with the harness, disconnect the electrical connector (4000KC-C) from
the FMU (4000KC) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the
connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(c) Do the electrical check of the channel B switch circuit in the overspeed valve Ref. ASM
73-25-18.
1 Make sure that contacts L and K are not shorted to ground.
2 Make sure that contacts L and K are not shorted to any other contacts in the connector.
3 Make sure that the resistance from contact L to contact K is between 0 and 10 ohms.
4 If a problem was found, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
(d) If no problems were found, disconnect the electrical connector (4000KS-J8) from the EEC
(4000KS) Ref. AMM 71-50-00-210-010 . Examine the male and female parts of the connection:
1 Examine the pins and sockets (contacts) for alignment and damage.
2 Look for contacts pushed rearward into the connector face.
3 Look for elongated sockets in the connector.
NOTE: This can be done by inserting a harness connector pin into each suspect socket. You
must feel friction when inserting and removing the pin.
4 Repair as necessary.
(e) Do the electrical check of the switch wiring in the channel B harness. Look for:
1 Wire-to-wire shorts and shorts to ground
· Wire-to-wire short check: Measure the resistance between the wires. If the resistance is
below 100000 (100K) ohms, then the wires are shorted and need to be repaired.
· Wire-to-ground short check: Measure the resistance between wire and engine metal or
ground. If the resistance is below 100000 (100K) ohms, then the wire is shorted to ground
and needs to be repaired.
2 Continuity
· Continuity check: Measure the resistance between the ends of the same wire. If the
resistance is above 10 ohms, then the wire needs to be repaired.
NOTE: An incorrectly wired harness can cause this problem. When testing these circuits,
make sure that the contacts are in the correct positions in each connector as specified
in the wiring diagram.
Overspeed Valve Switch Circuit Channel B Harness
FMU (4000KC) EEC (4000KS)
4000KC-C 4000KS-J8
Contacts Contacts
L Y
K Z
3 If a problem exists with the harness, repair or replace as necessary Ref. ASM 73-25-18.
(f) Install all removed connectors Ref. AMM 70-23-15-912-010 .
(g) Do the test for the fault, listed in Para 3 for fault confirmation.
1 If the test does not give the fault acronym OSFLCL, return the engine to service.
2 If the test gives the fault acronym OSFLCL, remove and replace the FMU ( 4000KC ) Ref.
AMM 73-22-52-000-010 and Ref. AMM 73-22-52-400-010 .
3 If this fault continues, remove and replace the EEC ( 4000KS ) Ref.
AMM 73-22-34-000-010 and Ref. AMM 73-22-34-400-010 .
5. Close-up
Subtask 73-22-00-860-067-A
A. Put the aircraft back to its initial configuration.
(1) Close the thrust reverser halves, activate the thrust reverser HCU, close the fan cowls and remove
the warning notices Ref. AMM 71-50-00-210-010 .
(2) On the ECAM control panel, set the UPPER DISPLAY and LOWER DISPLAY potentiometers to OFF.
Ref. AMM 31-60-00-860-002 .
(3) On the overhead panel 50VU, push the ENG FADEC GND PWR 2 pushbutton switch.
(4) De-energize the aircraft electrical circuits
Ref. AMM 24-41-00-862-002 . [Rev.6 from Feb 2017] 2026.04.04 04:36:17 UTC