What was found
INVESTIGATED PILOT REPORT OF BOTH MWS ANNUNCIATORS NOT ILLUMINATING AND FLASHING DURING PRE-FLIGHT TESTS OF ENG NR 1 AND ENGINE NR 2 ENGINE FIRE WARNING SYS TESTS. ALSO NOTED BOTH MWS ANNUNCIATORS WOULD NOT FLASH WHEN ANNUNCIATOR OVERIDE SWITCH MOVED FROM DIM OVERIDE TO NORMAL POSITION. CONFIRMED FAULT INDICATIONS. VERIFIED DA/L PANEL CIRCUIT BOARDS "G" AND "AF" INPUTS AND CONNECTOR CONDITIONS OK. IAW TECH SUPPORT, THE PN 25-6NF1909-43A CIRCUIT CARD "G" HAS DESIGN FAULT THAT CAN CAUSE REPORTED INDICATED CONDITION. REPLACED THE DA/L PANEL "G" CIRCUIT BOARD ASSY WITH NEW PN 25-6NF1909-63A CIRCUIT BOARD. MWS AND ENGINE FIRE TEST ANNUNCIATOR INDICATIONS NORMAL. RECOMMEND AIRFRAME MFR OFFER THE IMPROVED PN 25-6NF1909-63A CIRCUIT BOARD UNDER A RECOMMENDED SB OR MODIFICATION.