why does cool air come from hvac when lowered by 1 degree from HI? on 2004 Kia Amanti

When heater control unit is set to Hi, lots of heat, lower it by 1 degree, cool air starts to come from vents or floor. Keep lowering the temp, no difference. I have not scanned it yet for codes. It has an automatic HVAC with duel controls, the temp it the same on both sides.
Any suggestions?
Thank you

Asked by for the 2004 Kia Amanti
0 answers