Passenger side floorboard winds up soaked after rain even though we've put a tarp across the front of the car. Suspect a/c as well and heavy rain may have been coincidence. Ideas? Thanks!

My Dad's car had this one. He ended up replacing the rusted out heater fan three times before getting me to investigate. Every time it rained (hard) or he took it through the car wash the passenger side carpet would end up soaked. It may not necessarily be the problem with yours but it's something you can check. Turns out the outside air intake for the heater/vent is located in the windshield wiper well, passenger side. You will have to raise the hood and remove the protective grill that covers this area. This well also channels rain water coming off the windshield out through a drain near the side of the car (sometimes this drain can become plugged with leaf debris and / or algae - something else to check while you are at it), and if your tarp did not cover the top of the car your water may have also come from windshield run off. On my dad's car was a 4", square rubber doughnut around the heater intake that is supposed to prevent the runoff water from entering the intake. It had weathered, and along with a slightly botched windshield replacement become misshapen and no longer made a good seal allowing water to run under the gasket into the fan motor and onto the floor. The best fix for this was to replace the gasket but a little creative silicone application might fix it "for now".