Climent control temperature problem.

[Ed]

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