What was found
WHILE FLYING THROUGH RAIN IN IFR CONDITIONS, THE LANDING GEAR NOT DOWN/LOCKED WARNING HORN SOUNDED FALSELY EVEN THOUGH THROTTLE WAS NOT RETARDED TO DESCENT CONFIGURATION. AIRCREW PULLED WARNING HORN CIRCUIT BREAKER TO TEMPORARILY CANCEL THE HORN WHICH ALSO DEACTIVATES THE NORMAL FUNCTION OF THE STALL/GEAR WARNING SYSTEM. THE HORN IS VERY LOUD INTERFERING WITH ATC COMMUNICATIONS DURING A CRITICAL PHASE OF FLIGHT. TROUBLESHOOTING REVEALED THE THROTTLE SWITCH INPUT ON THE DUAL WARNING UNIT IS HYPERSENSITIVE TO A HIGH RESISTANCE GROUND, I.E. MOISTURE ACCUMULATION AT THE THROTTLE SWITCH TERMINAL.