WHILE DESCENDING THRU 12,000 FT APRX 40 MI EAST OF SAN DIEGO, CA, THE LEFT OVERWING EVACUATION SLDE ANNUNCIATOR LIGHT ILLUMINATED. THE SLIDE SEPARATED FROM THE ACFT APRX 7 MI EAST OF THE ARPT. NO FLT CONTROL PROBLEMS WERE NOTED. INTEGRITY OF THE SYS WAS FOUND TO BE SATISFACTORY. THE EVACUATION SLIDE SQUIB & ACTUATOR HAD NOT BEEN ACTIVATED. THERE WERE INDICATIONS THAT THE INTEGRATOR LOCKING PIN HAD NOT BEEN FULLY SEATED, WHICH ALLOWED THE LATCH SHAFT TO MOVE AFT, THUS ALLOWING THE DOOR LATCHES TO RELEASE. DURING A MODIFICATION ON 1/22/83, THE LATCH ATTACH SCREWS HAD BEEN CHANGED. THIS MODIFICATION REQUIRED UNLATCHING THE LOCK PIN. AMBIGUITIES WERE FOUND IN THE INSTALLATION PROCEDURE FOR THE OFF- WING SLIDE; THE INSTRUCTIONS FAILED TO DESCRIBE THE MODE OF OPERATON WITH RESPECT TO TURNING DIRECTIONS OF THE LATCH- UNLATCH LEVERS. THIS WAS THE 4TH IN-FLT OVERWING SLIDE DEPLOYMENT. AS A RESULT OF THIS INCIDENT, BOEING BEGAN A DESIGN CHANGE OF THE INTEGRATOR MECHANISM. IN THE INTERIM, COMPLIANCE WITH SB 767-25-5 WAS REQUIRED BY 2/15/83.