condensation on inside of windshield
1). HVAC drain clogged.
2). Using recirculate mode when using heater.
3). Moisture in the carpets.
4). Condensation was installed wrong, it should be on the exterior.
Same symptom on a recent Car Talk podcast. In that case Ray and Tom thought it was a leaking heater core. Does inside of windshield feel a little greasy, has sweet aroma?
Put convertible top up
Aaahh, now I see how the condensation gets inside. It may not have been installed wrong. My mistake.