Hi, I have a 2001 Volvo S40. The other day I notice the air through the vents got really hot. Just like I had put the heat on high. I turned the temp knob from the extreme bottom setting (blue color) to 78 then back down. The temperature seemed to go back to what should have been coming out the vent which was outside air. Any one have this problem before or an idea what I should check? Thanks, Ed