Thanks for the reply. The car is still in the shop. With respect to the carpet, I had a carpet mat on the floor. I took it out after it got wet. Subsequently, after the heater core replacement, I vacuumed the floor a few times. It didn?t seem wet at that time. When I get the car back, I?ll check again. I kind of doubt that the smell is coming from there though. The smell seems to happen when I have both the heat and the fan on, and whether the fan?s dial is pointed up, down, or to the side. The fan seems to be the biggest reason. It?s been two weeks since the replacement and I?ve had the heat and fan on a number of times.