I have recently been having problems with my heat and A/C. It is a 99 Concorde LXi 3.2L. It seems to come and go. Sometimes the heat works, and other times it doesn't. Like tonight, heat no worky, yesterday, works like a charm, and the day before that, no heat again. My A/C did this in the summer on and off too. An ideas? I was thinking thermostat, but maybe more than that? Also, it doesn't matter where I have the temp. set to, it blows one kind of air and that is it, medium warm air. It's winter and I want to be warm! Please help! Thanks!