A Fuse In One Of The Center-Tank Fused Adaptors Has Operated More Than One Time

TASK 28-42-00-810-881-A
A Fuse In One Of The Center-Tank Fused Adaptors Has Operated More Than One Time

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

WARNING: WHEN YOU DO WORK ON THE FUEL SYSTEM WIRING, YOU MUST USE TEST EQUIPMENT THAT IS APPROVED (REFER TO INTERNATIONAL OR NATIONAL SPECIFICATIONS FOR INTRINSICALLY SAFE TEST EQUIPMENT: EN50020, UL913 OR EQUIVALENT). TEST EQUIPMENT THAT IS NOT APPROVED CAN CAUSE FIRE OR AN EXPLOSION.

1. Possible Causes

This procedure is not a full list of all the items (and LRUs) that can cause a fuse link in a center-tank fused adaptor to operate
It is a guide to logical troubleshooting to find the possible cause and emphasize some troubleshooting steps previously given

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	MULTIMETER - STANDARD

B. Referenced Information

REFERENCE	DESIGNATION
ESPM 2031350
ESPM 2052210
ESPM 2053210
AMM 28-42-00-740-001	Status Report (BITE)
ASM 284209
AWM 940003

3. Fault Confirmation
Subtask 28-42-00-710-124-C ** ON A/C NOT FOR ALL

A. Test
(1) Not applicable.

4. Fault Isolation
Subtask 28-42-00-810-139-C ** ON A/C NOT FOR ALL

A. Procedure

NOTE: This procedure is not a full list of all the items (and LRUs) that can cause a fuse link in a center-tank fused adaptor to operate. It is a guide to logical troubleshooting to find the possible cause and emphasize some troubleshooting steps previously given .

(1) If the identification of the fuel-quantity probe to the fuse link that has operated:

is known, do step (3)
is not known, do step (2).

(2) Do the applicable test that follows on the applicable fused adaptor. The test in:

the step (a) is for the adaptor 7509VC-A/B
the step (b) is for the adaptor 7512VC-A/B.

(a) Do a check for continuity ESPM 2052210, with a MULTIMETER - STANDARD, between the pins given in the table that follows.
1 Table 1 - Is applicable to a fused adaptor 7509VC-A/B.

OPERATED FUSE LINK	RELATED FUEL-QUANTITY PROBE
T -- -- T	CTR TK QTY PROBE 38QT
U -- -- U	CTR TK QTY PROBE 37QT
V -- -- V	CTR TK QTY PROBE 36QT
W -- -- W	CTR TK CADENSICON 20QT

NOTE: The FUSED ADAPTOR 7509VC-A/B is related to the:

main wire routing 1S left side AWM 940003
pressure seal (feedthrough) 7505VP
receptacle 7509VC ASM 284209
harness 17QT
center tank group A fuel-probes.

2 Make a record of the fused wiring link that shows an open circuit.
(b) Do a check for continuity ESPM 2052210, with a MULTIMETER - STANDARD, between the pins given in the table that follows.
1 Table 2 - Is applicable to a fused adaptor 7512VC-A/B.

OPERATED FUSE LINK	RELATED FUEL-QUANTITY PROBE
D -- -- D	CTR TK QTY PROBE 39QT
T -- -- T	CTR TK QTY PROBE 35QT
V -- -- V	CTR TK CIC 39QT

NOTE: The FUSED ADAPTOR 7512VC-A/B related to the:

main wire routing 2S right side AWM 940003
pressure seal (feedthrough) 7510VP
receptacle 7512VC ASM 284209
harness 18QT
center tank group B fuel-probes.

2 Make a record of the fused wiring link that shows an open circuit.
(3) Get the applicable TSM Task for the identified fuel-quantity probe.
(4) Read all of this step before you do more work. This is important if this is the second or subsequent time a fuse link (in the fused adaptor) has operated.
(a) Severe (Wet) Weather
1 Read the ESPM topic Severe Weather And Moisture Prone (SWAMP) areas on the aircraft ESPM 2031350
(b) Visual Inspections
Good lighting must be used to do all the visual inspections.
(c) The Repairs (of unserviceable wiring and connectors)
The repair(s) must be fully done with reference to the applicable topic in the Electrical Standard Practices Manual (ESPM). After the repair is fully completed the applicable wiring test must be done again.
(d) The Fuel Condition
The fuel-tanks must contain a minimum of:

water
debris (unwanted material).

Water in the fuel can cause microbiological contamination. Make sure that all the Maintenance Planning Document (MPD) scheduled servicing tasks (related to water and microbiological contamination) have been correctly done.

Debris (unwanted material). It is a possibility that a metallic object can cause a short circuit between the two concentric tubes, or the terminals, of a fuel-probe. Example, a small piece of a single strand of wire from a multi-strand larger wire. A metallic object can stay in one location for a period of time and then start to move about in the fuel-tank and possibly cause a short circuit.
(5) Do the applicable TSM Task for the identified fuel-quantity probe. Make sure that all the steps given in the FQIS fault isolation task/procedure are fully done.
(6) If the fault continues:
(a) Investigate the possibility of an apparent unrelated fault (in a different system) at the same time.

NOTE: The aircraft cable routes for the FQIS are installed in conduit/harness assemblies which contain wires used for other aircraft systems. The in-line fused adaptors are to prevent short circuit conditions that if continued can cause in-tank components to overheat with the risk of fire or explosion.

1 Troubleshoot the related fault symptom(s), if necessary.
a See step (8) for the procedure to follow to get a list of wires that are installed parallel for part of the route from the main landing gear bay and enter the aircraft fusalage at the pressure seal/feed thru 7505VP (1S left side) or 7510VP (2S right side).
(b) Investigate the possibility that work or a repair that has been done in adjacent wiring or system has caused damage and given this fault.
1 Troubleshoot the related fault symptom(s), if necessary.
(7) If the fault continues:
(a) Do a visual inspection and electrical aircraft wiring checks of the main wire routing as follows AWM 940003:

for fused adaptor 7509VC-A/B, between the connector 7509VC1-A and the FQIC rack connector 3QT-A, is electrical wiring route 1S (sensitive system 1)
for fused adaptor 7512VC-A/B, between the connector 7512VC1-A and the FQIC rack connector 3QT-A, is electrical wiring route 2S (sensitive system 2).

(b) Repair (or replace) all the unserviceable wiring and connectors ESPM 2053210.
(c) Do a wiring test of the repaired (or replaced) wiring and connectors.
(d) Do a Status Report (BITE) (Test of the FQIS) AMM 28-42-00-740-001.
(8) Do a search of:

the Aircraft Wiring List (AWL) in the aircraft master wire list (Ref. AWL 91-90) for the wires related to (that pass through) the equipments 7505VP and 7510VP (hookup list).

OR, if available
the Dynamic Wiring option for the wires related to (that pass through) the equipments 7505VP and 7510VP.

NOTE: The wire identity is given by a four digit ATA code and a four digit number, an example of which follows.

WIRE IDENT	EQUIPMENT FIN
2846-5881	7505VP

[Rev.8 from Aug 2018] 2026.04.04 04:29:11 UTC