What was found
ERRONEOUS EVAC HORN WHILE ON DESCENT (~15,000 FT). ONLY INDICATION ON FLIGHT DEC WAS EVAC CMD GUARDED SWITCH LIGHT ILLUMINATED. HORN CONTINUED ALL THE WAY UNTIL SHORTLY PRIOR TO LANDING. CORRECTIVE ACTION: PERFORMED EVAC HORN OPS TEST REF A220 AMP 44-11, TEST WOULD FUNCTION CORRECTLY BUT ONE SPEAKER IN THE AFT CABIN WOULD NOT TURN OFF. REPLACED CABIN CONTROLLER BOX AND COMPLETED CORE SOFTWARE LOAD THROUGH STEP 10 Y. REF A220 AMP 44-11-90-90004- 750A-A (DF694655) C/W CMS CYBER SECURITY LOAD 1)K TO AH (3). READDRESS PROCEDURE FAILED ZONE 2. SLAVED IN NEW ZONE BOX 2 NO HELP. PER AMP 44-11. CHKD CONTINUITY OF WIRING FROM PSUC A4412P1 TO PSUC A4426P1 READING NML. VERIFIED ZONE FAILING READDRESS RUNS TO ZONE BOX 1 IN DIAGRAM SUSPECT ZB1 ISSUE OR POSSIBLY S/W RELOAD (OM 233767) FULLY INSTALLED NEW ZONE 1 BOX PER A220 AMP 44-11-07. THE RED ZONE FROM ABOVE, THE CALL & PERSONAL LIGHTS ARE WORKING BUT STILL RED. FOR THE READDRESS PROC (RH 177277) RELOADED CMS CORE SW PER A220 AMP 44-11-90-90004-750A-A UP TO STEP AD. R/R ZB 2 PER A220 AMP 44-11. (RM 716289). FOUND OPEN BETWEEN J4046 PINS A-3 TO 4202P1 PIN 10 AND J4046 PIN A-4 TO 4202P1 PIN 9 (TN 313816) PERFORMED SUCCESSFUL READRESS PER AMP 44 -11-00. ZB 1 AND 2 BOTH PASS. JJ 868406. RECHEKED WIRE RUN J4046 TO 4202P1 FOUND NO OPENS. RECHECKED MULTIPLE TIMES WHILE SHAKING HARNESS WITH NO TROUBLE. CONTINUED WITH SOFTWARE LOAD PER A220 AMP 44-11 STARTING AT STEP 1.AD. LOAD COMPLETE OPS TEST OF CMS AND CABIN CONTROLLER PER AMP 44-11. OPS NML. OPS OF EVAC HORN 44-11-17. OPS NML. ALL SPEAKERS TURN OFF. AC OK FOR SVC. (LP#8792318; AIRCRAFT WAS GROUNDED)