L(R) Underfull Level Sensor 3 26QJ1(2)

TASK 28-46-00-810-810-A
L(R) Underfull Level Sensor 3 26QJ1(2)

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

FLSCU-1 [7QJ]
FLSCU-2 [9QJ]
aircraft wiring
HARNESS-CHAN B, L WING TK INR [14QT1]
HARNESS-CHAN B, R WING TK INR [14QT2]
SENSOR-UNDERFULL, L WNG TK INR 3 CHANNEL B [26QJ1]
SENSOR-UNDERFULL, R WNG TK INR 3 CHANNEL B [26QJ2]
HARNESS-LEFT WING TANK B [63QT]
HARNESS-RIGHT WING TANK B [64QT]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 28-46-00-810-818-A	FLSCU1(2) 7QJ(9QJ)
ESPM 2053210
AMM 28-10-00-910-001	Safety Procedures When You Do Work in a Fuel Tank
AMM 28-10-00-910-002	Access to the Fuel Tanks and the Work Areas
AMM 28-42-43-000-005	Removal of the Wing Tank Harness
AMM 28-42-43-000-007	Removal of the Wing-Tank Inner-Cell Group B Harness
AMM 28-42-43-000-008	Removal of the Wing Tank Fuel Quantity Indicating Probe Fused/Shorting Plug Connectors
AMM 28-42-43-400-005	Installation of the Wing Tank Harness
AMM 28-42-43-400-007	Installation of the Wing-Tank Inner-Cell Group B Harness
AMM 28-46-00-740-001	Functional (BITE) Test
ASM 284603
AWM 284607
AWM 284608
AWM 284610
AWM 284611
AWM 284612
AMM 28-46-15-000-001	Removal of the Wing-Tank Fuel-Level Sensors
AMM 28-46-15-400-009	Installation of the Wing-Tank Fuel-Level Sensors
AMM 28-46-34-000-001	Removal of the Fuel-Level Sensing Control-Unit (FLSCU)
AMM 28-46-34-400-001	Installation of the Fuel-Level Sensing Control-Unit (FLSCU)

3. Fault Confirmation
Subtask 28-46-00-740-059-C ** ON A/C NOT FOR ALL

A. Test
(1) Do the BITE test of the FLSS AMM 28-46-00-740-001.
(2) Examine the FLSS STATUS page on the MCDU.
(3) If the page shows messages for one or more of the other sensors and/or the FLSCU-1(2), do (Ref. TSM TASK 28-46-00-810-818).
(4) If the message 284615 L(R) UNFULL SENSOR 26QJ1(2):

is shown, do Para. 4.A.
is not shown, no work steps are necessary.

NOTE: You can get more data from the:

Aircraft Maintenance Manual (AMM) Chap. 28-46-00, the Fuel Level Sensing System, Description and Operation (D and O)
Trouble Shooting Manual (TSM) - Task Supporting Data (Ref. P. Block 301)
Aircraft Schematic Manual (ASM) ASM 284603.

You can get more Trouble-shooting data from the CFDS(FUEL):

Input Parameters Page 3 (Ref. P. Block 301), used with the Fuel Level Sensors Operating (Changeover) Values (Ref. P. Block 301)
FLSCU Trouble-shooting Data (Ref. P. Block 301).

NOTE: OPTIONAL TESTING:
Where a PSD A320-2 Fuel Level Sensing Test Set is available measurements can be taken before a decision is made to go into or close up a fuel tank. The Test Set enables the tank mounted components and tank wiring to be tested from the tank wall connectors.

Subtask 28-46-00-740-059-D ** ON A/C NOT FOR ALL

is shown, do Para. 4.A.
is not shown, no work steps are necessary.

NOTE: You can get more data from the:

Aircraft Maintenance Manual (AMM) Chap. 28-46-00, the Fuel Level Sensing System, Description and Operation (D and O)
Trouble Shooting Manual (TSM) - Task Supporting Data (Ref. P. Block 301)
Aircraft Schematic Manual (ASM) ASM 284603.

You can get more Trouble-shooting data from the CFDS(FUEL):

Input Parameters Page 3 (Ref. P. Block 301), used with the Fuel Level Sensors Operating (Changeover) Values (Ref. P. Block 301)
Trouble-shooting Data (Ref. P. Block 301).

NOTE: OPTIONAL TESTING:
Where a PSDA321-1 Test Set is available, a check can be made before a decision is made to go into or close up a fuel tank. The Test Set enables a GO/NOGO check to be made of the tank mounted components and wiring from the tank wall connectors.

4. Fault Isolation
Subtask 28-46-00-810-059-C ** ON A/C NOT FOR ALL

A. Procedure
(1) Do the steps applicable to the test equipment available.
(2) Test Equipment.

(a) If there is:

approved test equipment available, go to Step (3)
no approved test equipment available, go to Step (6).

(3) Get access to the tank wall connector 4040VC1(2)-A (for the wing tank harness 14QT1(2)) AMM 28-42-43-000-008.
(4) Disconnect the free connector 4040VC1(2)-A from the receptacle 4040VC1(2).
(5) Do a resistance check of the sensor 26QJ1(2) at the tank wall connector 4040VC1(2) between pins <D and <C AWM 284607 ( AWM 284608).
Make sure the resistance is between 330 and 480 ohms.
If there is:

continuity as specified above, go to Step (6)
no continuity as specified above (resistance check out of range), go to Step (8).

NOTE: The sensor status (wet or dry) and fuel/air temperature will have an effect on the resistance value.

(6) Replace the FLSCU-1 [7QJ] ( FLSCU-2 [9QJ] ) AMM 28-46-34-000-001 and AMM 28-46-34-400-001.
(7) If the fault continues:
(a) Get access to the tank wall connector 4040VC1(2)-A (for the wing tank harness 14QT1(2)) AMM 28-42-43-000-008.
(b) Disconnect the free connector 4040VC1(2)-A from the receptacle 4040VC1(2).
(c) Do a check AWM 284607, and AWM 284608 of the aircraft wiring (sensor input line - H) between the FLSCU-1(2) rack connector AB, pin 10D and the tank wall free connector 4040VC1(2)-A, pin <D.
(d) Do a check AWM 284607, and AWM 284608 of the aircraft wiring (sensor input line - L) between the FLSCU-1(2) rack connector AB, pin 10C and the tank wall free connector 4040VC1(2)-A, pin <C.
(e) Do a check AWM 284611 of the aircraft wiring (FLSCU-1 BITE 4 test command line) between the FLSCU-1 rack connector AA, pin 15D and the FQIC rack connector AB, pin 7K or the ( AWM 284612 of the aircraft wiring (FLSCU-2 BITE 4 test command line) between the FLSCU-2 rack connector AA, pin 15D and the FQIC rack connector AB, pin 9H.
(f) Do a check AWM 284610 of the aircraft wiring (FLSCU-1 LS15 output line) between the FLSCU-1 rack connector AB, pin 3D and the FQIC rack connector AB, pin 5H or the (aircraft wiring (FLSCU-2 LS15 output line) between the FLSCU-2 rack connector AB, pin 3D and the FQIC rack connector AB, pin 14H).
(g) Repair all the unserviceable wiring and connectors ESPM 2053210.
(h) Connect the free connector 4040VC1(2)-A to the receptacle 4040VC1(2).
(i) Do the test in Para. 3.A.
(8) If the fault continues or if there is no continuity in Step (5):
(a) Drain, open and vent the tank AMM 28-10-00-910-001 and AMM 28-10-00-910-002.
(b) Do a wiring check of the HARNESS-CHAN B, L WING TK INR [14QT1] ( HARNESS-CHAN B, R WING TK INR [14QT2] ) AWM 284607 ( AWM 284608) and replace, if necessary AMM 28-42-43-000-007 and AMM 28-42-43-400-007.
(c) If the harness is serviceable, replace the SENSOR-UNDERFULL, L WNG TK INR 3 CHANNEL B [26QJ1] ( SENSOR-UNDERFULL, R WNG TK INR 3 CHANNEL B [26QJ2] ) AMM 28-46-15-000-001 and AMM 28-46-15-400-009.

Subtask 28-46-00-810-059-E ** ON A/C NOT FOR ALL

A. Procedure
(1) Do the steps applicable to the test equipment available.
(2) Test Equipment.

(a) If there is:

approved test equipment available, go to Step (3)
no approved test equipment available, go to Step (6).

(3) Get access to the tank wall connector 4040VC1(2)-A (for the wing tank harness 63QT(64QT)) AMM 28-42-43-000-008.
(4) Disconnect the free connector 4040VC1(2)-A from the receptacle 4040VC1(2).
(5) Do a resistance check of the sensor 26QJ1(2) at the tank wall connector 4040VC1(2) between pins <D and <C AWM 284607 ( AWM 284608).
Make sure the resistance is between 330 and 480 ohms.
If there is:

continuity as specified above, go to Step (6)
no continuity as specified above (resistance check out of range), go to Step (8).

NOTE: The sensor status (wet or dry) and fuel/air temperature will have an effect on the resistance value.

(6) Replace the FLSCU-1 [7QJ] ( FLSCU-2 [9QJ] ) AMM 28-46-34-000-001 and AMM 28-46-34-400-001.
(7) If the fault continues:
(a) Get access to the tank wall connector 4040VC1(2)-A (for the wing tank harness 63QT(64QT)) AMM 28-42-43-000-008.
(b) Disconnect the free connector 4040VC1(2)-A from the receptacle 4040VC1(2).
(c) Do a check AWM 284607, and AWM 284608 of the aircraft wiring (sensor input line - H) between the FLSCU-1(2) rack connector AB, pin 10D and the tank wall free connector 4040VC1(2)-A, pin <D.
(d) Do a check AWM 284607, and AWM 284608 of the aircraft wiring (sensor input line - L) between the FLSCU-1(2) rack connector AB, pin 10C and the tank wall free connector 4040VC1(2)-A, pin <C.
(e) Do a check AWM 284611 of the aircraft wiring (FLSCU-1 BITE 4 test command line) between the FLSCU-1 rack connector AA, pin 15D and the FQIC rack connector AB, pin 15E or ( AWM 284612 of the aircraft wiring (FLSCU-2 BITE 4 test command line) between the FLSCU-2 rack connector AA, pin 15D and the FQIC rack connector AB, pin 13E).
(f) Do a check AWM 284610 of the aircraft wiring aircraft wiring (FLSCU-1 LS15 output line) between the FLSCU-1 rack connector AB, pin 3D and the FQIC rack connector AC, pin 2A or the (aircraft wiring (FLSCU-2 LS15 output line) between the FLSCU-2 rack connector AB, pin 3D and the FQIC rack connector AC, pin 4E).
(g) Repair all the unserviceable wiring and connectors ESPM 2053210.
(h) Connect the free connector 4040VC1(2)-A to the receptacle 4040VC1(2).
(i) Do the test in Para. 3.A.
(8) If the fault continues or if there is no continuity in Step (5):
(a) Drain, open and vent the tank AMM 28-10-00-910-001 and AMM 28-10-00-910-002.
(b) Do a wiring check of the HARNESS-LEFT WING TANK B [63QT] ( HARNESS-RIGHT WING TANK B [64QT] ) AWM 284607 ( AWM 284608) and replace, if necessary AMM 28-42-43-000-005 and AMM 28-42-43-400-005.
(c) If the harness is serviceable, replace the SENSOR-UNDERFULL, L WNG TK INR 3 CHANNEL B [26QJ1] ( SENSOR-UNDERFULL, R WNG TK INR 3 CHANNEL B [26QJ2] ) AMM 28-46-15-000-001 and AMM 28-46-15-400-009.

[Rev.8 from Aug 2018] 2026.04.04 04:29:15 UTC