Pontiac Repair: Water leaking into passenger compartment, grand am gt, weather strips

Question
I have a 2000 Pontiac Grand AM GT that has a water leak into the passenger compartment.  It appears to be leaking into the floor pan under the plastic floor/door trim about midpoint.  It does this only when the car is setting when it rains.  Have not noticed the leak as long as you are driving.  I have heard about replacing door seals, resealing pillar seams, resealing around a/c grille at windshield.  I have had the windshield replaced, but that was not the problem.  Where is the best place to start in trying to stop the leak.

Answer
Hi Sherry:

The most common thing is the water barrier inside the doors. If this is a 2 door for sure that's where I would start. try this open one of the doors and with a garden hose on slowly run water along the door glass bacj and forth for a minute or to and then bend down and look to see if there is water running out between the door and the inside door trim. if so that's the leak. You will see water running out of the drain holes in the bottom of the door this is normal but the water should not be comming out from anywhere else. Water leaks are really hard to find but that is the most common place on that car. Other things I have sen are trunk weather strips but the trunk would be wet as well. If this car has a sun roof I have see issues with the drain hoses comming off and causing a leak as well. Just a few places to look and good luck :}