Hi, I live on the northeast edge of phoenix Arizona, Will be driving to UTAH this weekend - so i MAY experience using heat for the first time. I will tell you, I use AC...All the time. This week and last; weather was cool - been using NO AC...- but cannot use outside air...coz. Get in the Car - turn it on - Smell. Turn ON In Car Circulation - smell goes away instantly. (why in car circ does not stay on when i turned car off with it on, i do not know) I have read posts - AC off (appears off for a while - drove 40 miles) Outside air on - no smell (I cannot take 10 minutes of that smell - have not tried prolonged exposures w/ AC off) I have also read posts - from a guy who before he gets to his destination - he turns off AC -and runs the blower full (to dry up any condensation) - also has no issues. Personally - with AC on (or off) - no smell w/ In car circ. This is not consistent w/ posts i have read. I have no experience w/ heat - although its hard to believe you would have this problem with heat...Do you? It still appears to me to be a mold issue though some external air vent. I think heat would kill it - be manufactured or just lovely phoenix oven air. I'll try the heat when in Utah. Let you know how it goes.