Oldsmobile/Buick Repair: Water on left side of floor board, water coolant, engine coolant

Question
I have a 1992 Buick Century Special with a 3.3 engine with air.  For the past few weeks, the drivers side floor board has been wet.  The other day I turn off the heater and now the floor board is dry.  I can't understand why this is happening.  I assumed the heater core would leak on the passenger's side if it was bad.
Can you offer any advice as to what might be going on to cause this?  Could the core need replacing?  I priced the core and at Advanced Auto it is $27.95 but the labor is $150.00 to replace it.  I will appreciate you advice and recommendations on this issue.  Thanks again,  Stephen

Answer
HI STEPHEN, WELL I DO NOT FEEL THE HEATER CORE IS THE PROBLEM. IF IT WERE THE PASS SIDE OF THE FLOOR WOULD BE WET OF COOLANT NOT WATER. TOUCH THIS AND SEE IF IT FEELS LIKE COOLANT OR WATER. COOLANT WILL FEEL VERY SLIPPERY. BEING THAT IT IS ON THE DRIVERS SIDE I THINK THIS IS A WATER LEAK FROM THE FRONT WINDOW SEAL.. DRY THE FLOOR OUT AND HAVE SOMEONE GET IN THE CAR WHILE YOU TAKE A GARDEN HOSE AND SPRAY THE FRONT WINDOW AREA ALL OVER. IF IT GETS WET LIKE THIS, WHICH I THINK IT WILL, CALL A WINDOW COMPANY OR COLLISION SHOP AND HAVE THEM RESEAL THE FRONT WINDOW.. THIS IS VERY COMMON..IF THE CORE WAS LEAKING THE ENGINE COOLANT WOULD GET LOW AND IT WILL NOT MATTER IF THE HEATER IS ON OR OFF. THE HEATER CORE IS ALWAYS UNDER PRESSURE WHEN THE CAR IS RUNNING..THE HEATER CONTROLS HAVE NO EFFECT ON THIS AT ALL...LET ME KNOW HOW THIS GOES AND GET BACK TO ME IF NEED BE..GOOD LUCK TO YOU,,,TOM..