I've got a 2002 TL and have been noticing spots on the inside of the windshield above where the vents are (next to the windshield). I took it to the dealer and had them look at it, they said nothing was wrong, but that I probably had dash cleaner (e.g. Armourall) in the vents. I told the service guy that I don't use Armourall and I only spray my dash cleaner on the rag, not directly onto the dash.

Any idea what it could be? They said they checked and it wasn't radiator fluid, so the heater core wasn't bad.

Thanks!