Use header + air con, I used only air con before and I got a fever the next day when the temperature is 6 degrees raining.. Also, switch off the interal air circulation button (the recursive arrow key), this allows the cold air to come in My car is Ascent with traditional air con knobs, but not sure how climate control system works in conquest and levin Yeah A/C on is a given! Just A/C on, let the air in from outside and you should be fine.