2001 - S40 having problems with the heat as it gets colder, the engine warms up, heat flows from the heater but after 15 minutes of travel the heater stops blowing hot air and blows cold air, the heat does come back occasionally, changing the temperature setting does not help. Is there a way to re-calibrate all the temperature sensors that relate to the heater?

 

Is this with the fan speed dial in auto? If so make sure it's all the way left. On mine if I bump the fan speed out of auto it will sometimes start and stop blowing randomly. I turn it all the way left then give it just a little extra "umphh". Not much, just a little more than simply turn it left. You don't want to break it off.

 

No, this is not about the fan speed but temperature, you get hot air for a short time then it lets in outside air at 0 - 5 deg cel as that is the temp outside. Which holding your hand over an air vent will feel like freezing air.