I own a 2010 Corolla S which was bought used back in 2013. My first winter brought out the one major issue. There were multiple gaps in the electrical connections of the rear defroster lines which would leave wide swaths of icy, frosty glaciers on my rear window.
The previous owner must have physically scraped multiple areas or used a corrosive/harsh cleaning agent on the rear windshield.
I live in the Northeast so this was a problem, albeit not a major one. I used touch-up conductive paint to repair most of the connections which now seem to be working adequately. However, there's still a large swath at the top of the windscreen that is still not defrosting... despite my best efforts with a voltmeter to find the poor connection.
Due to my OCD tendencies, was thinking to eventually replace the rear windshield...Has anyone had any experience with replacing the rear windshield?