Add me to the list of people dealing with this annoying issue. All the windows, all the time. HATE HATE HATE.
At first, I thought it might be Armor All used on the dash vaporizing in the 150*+ interior temps the car sees in Phoenix. I haven't wiped the dash with anything other than water in something like three months. Still shows up daily. I've also wondered if it was the dash materials breaking down. The glue holding things together breaks down, so perhaps there's a side effect to that?
I used a Lexol brand leather cleaner/conditioner that left the seats very tacky and didn't want to buff off easily. I guess I could pull the seats, clean the windows, and let it sit in the sun for a weekend to see if the conditions improve, but I dunno. A lot of work for such a stretch of a hypothesis. Even so, there are "essential oils" in leather conditioners, right?
It *could* be heater core leak. I'll have to poke around and see if there's any leakage inside the car. Despite replacing radiator/cap/tstat/waterpump/hoses under the hood, I still seem to be losing coolant over about a 2-3 week time frame. I see some mention here of looping out the heater core, but there would still be residue in the core and/or carpet/foam after-the-fact, right? Oh yeah, and I could have sworn I smelled coolant the other night leaving boostedinaz's place in the rain.
Whatever is causing this, I hate it.