My 2008 Chevy Equinox needed a new heater core installed. Only had the car for four years. The 2006 had a recall reference bulletin #11135. Why not the 2008?

in cold weather -20 cel. I have to keep heater mainly on defrost or front window starts to frost over and the side windows never defrost, except for a little area that you can see the outside mirrors through. I've had a Rendezvous for 6 years and never had this problem and it had a lot more window area than an Equinox. It doen't matter if I am alone in the vehicle or have passengers, I can't keep windows clear.