P/BSW (LED) FAULT Legends (With Lamp Drive Circuits in the FQIC 3QT P/N SIC5059-13-XX) Show Dimly When They Should be Off

TASK 28-42-00-810-876-A
P/BSW (LED) FAULT Legends (With Lamp Drive Circuits in the FQIC 3QT P/N SIC5059-13-XX) Show Dimly When They Should be Off

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

1. Possible Causes

2. Fault Confirmation
Subtask 28-42-00-710-117-B ** ON A/C NOT FOR ALL

A. General
(1) Read TFU 28.42.00.040 or if not available read the short extract that follows:

AIRBUS TFU : 28.42.00.040 short extract

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DESCRIPTION

Without push button (P/B) selection, a slight illumination of the cockpit

panel P/B switch 48QA (Auto feed fault P/B) was reported. The slight glow

can only be observed during specific lighting conditions

(example, at night). There is no associated warning.

CONSEQUENCES

There is no functional consequence. The partial P/B illumination can be

easily distinguished from the normal illumination. In addition no ECAM

warning is triggered.

INVESTIGATION STATUS

The FQIC provides a direct electrical grounding signal for the 5VAC Fault

caption on 48QA indicator through a lamp drive circuit. The lamp drive

circuit is modified in the new hardware FQIC standard PN SIC 5059-12-10

which introduces solid-state relays instead of electromechanical relays

(weight and reliability improvement).

In parallel, mod 31608 introduces LED cockpit P/B which has resulted in a

load change within the lamp drive circuit.

The slight glow can only be observed when FQIC SIC5059-13-10 is installed

on post mod 31608 aircraft. It was concluded that the lamp drive circuit

solid state device allows sufficient current to flow to slightly illuminate

P/B LEDs. The P/B LEDs are much more sensitive to small current than

filament lamps.

MAINTENANCE ADVICE

No additional maintenance action is required.

(2) No maintence work is necessary.

3. Fault Isolation
Subtask 28-42-00-810-133-B ** ON A/C NOT FOR ALL

A. Procedure
(1) Not Applicable.

[Rev.8 from Aug 2018] 2026.04.04 04:29:10 UTC