I first noticed the issue when the car began to fog up every night, eventually I checked under the floor mats, and bingo. The carpets were completely soaked. No matter how many times I try to dry up the carpets the moisture always comes back within a couple days. It is by far the most concentrated on the floor in the rear seat. I can't find anywhere that water could be entering from. I've checked the door and window seals, and figured I could rule out a/c leaks since that typically originates in the front passenger.
Any ideas what could be causing this issue? And how can I fix it?
My car has 78000 miles.
My car has an automatic transmission.
This is a common sign of a leaking heater core. The [heater core]((https://www.yourmechanic.com/services/heater-is-not-working-inspection) is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. Most heater cores are located on the passenger side of the firewall (behind the dash) of the vehicle. Due to this location, when they begin to leak, it is common for the floorboards to be wet with coolant leaking. As a result, this also causes very heavy fogging of the windows due to the moisture content inside the cab of the vehicle. I would suggest having an expert from YourMechanic come to your location to diagnose your heater core.