The heater in my Dodge Grand Caravan (2006) started being unreliable on Monday....usually by the time I hit the main road on my way to work I have to turn the heat down, but on Monday I noticed I was half way to work and still cold. I turned it up but it was blowing luke-warm air at best. It seems if I run it later in the day the heat works better, still not 100% but I'm not freezing. Its when I turn it on first thing in the morning when its been off all night that I seem to have the problem. The van isn't overheating - the temp gauge is fine. Is this an easy fix, or am I looking at $$$ ? More importantly, is it something that I have to get fixed ASAP before it leads to engine damage, or can I just put up with it until I can get it into a shop to get it fixed? Thanks!!