Hello to everyone. I am in need of a help on a peculiar problem. I have a new Seton W 90 (3 weeks running). I have an exchanger in my plenum on my updraft forced air furnace. When the furnace blower is off we get an odor in the vents above the furnace. The only thing that would be different is that the temp in the exchanger increases as it sets idle. It is a hot smell almost like plastic. I have taken side panel off of plenum and checked all over the furnace. You can only smell it through the vents in the house as it is rising with the heat. Has any one encountered this? I am going to turn it down to 160 degrees to see if it helps. Thanks in advance.