Noticed a 3 inch crack leading down from the rain sensor yesterday.  Can't feel it from within or without - it's within the glass.  My windshield is heated - wondered if something had happened in the recent hard frost/drop in temp.   Getting it sorted via windscreen insurance but flummoxed as to why.   Anyone else had this?

Sorry no idea,

but you are sure it is a crack & that it is not the black line of an aerial in the screen.

Definitely not a wire.  At first I thought it was a melting drop of ice running down the screen but it actually didn't move or change and can't be felt externally or internally.