[stvding]

First time it happened is last winter. After a car wash, I went to gym, parked outside. After finishing gym, I found out icing on the rear windshield. Didn't think it was a problem. Turned on rear windshield heating, but saw water dripping down. Finally, realize it was icing on the inside...damn.huge mass to clean up especially in a coupe! Had to climb back there and the windshield angle is terrible to reach..

I did not know what cause it until this June. I found out it was a leak! After my roof wrap, I did not seal the shark fin antenna properly. Therefore water is leaking into the cabin form moisture.

However, I bought windshield sealant to seal up the shark fin this June. Never any leak no more.

Then sh1t happen again this week!!! It became really cold this week in Ontario. below -15 C.
After parking outside for a few hours. The rear windshield again frost and iced inside!! Driver side front windshield and side window. rear 2 small windows. sunroof edge. all iced! wtf!!!

For the front, I can use the defroster blower. But rear, I just can't do anything without making a mess. However, I parked underground overnight. The icing is gone next morning.

I don't know what cause the icing. I bought a moisture grabber bag from homedepot and placed it at rear windshield. Did not help....

I googled a bit. Someone said heat core leak? leaking coolant into cabin? But I did not smell anything funny. Or is the shark fin seal broke?

Help!