What was found
GROUND HORN ALARM KEEPS GOING OFF WITH A/C POWER OFF AND GROUND POWER DISCONNECTED REFERENCE WDM 24-33-21-1, REMOVED RELAY K24019 IN P310 PANEL AND HORN STOPPED. RELAY IS DAMAGED AND SMELLS BURNT. OLD RELAY IS IN COCKPIT AND P310 PANEL IS OPENED. AIRCRAFT IS DEPOWERED AND TAGGED REPLACED GROUND POWER BATTERY RELAY REF AMM 24-33-07. REMOVED LOCKOUT TAGS AND CLOSED P310 PANEL. OPS CHECK FOR RELAY IS GOOD AT THIS TIME. NO GROUND HORN AFTER AIRCRAFT SHUTDOWN.