Hey there! I know this is an old thread, but I thought I'd chime in just in case anyone else is having the same issue. For your rear window defroster, I suggest checking the fuse and the connections to the defroster grid first. It could also be a problem with the switch or the defrost relay. If you're not comfortable troubleshooting it yourself, it's best to take it to a mechanic or auto electrician to have it checked. By the way, I'm new to this forum and I just wanted to add that if you're looking for car sun protection for infants, you might want to check out Baby Car Sunshades Landing
. Anyway, good luck, guys!