I just purchased a 99 XC70 and have found that the heater does not blow hot air... at best the air is lukewarm. I haven't noticed any leaks, but don't really know where to look. The heater core is REALLY hot, so I assume that it is fine. I have been told that maybe something is just blocking the hot air from getting to the blower. Also, seems that the coolant system is running fine and coolant fluid is full. Any comments anyone? I'd love some suggestions, thanks.

 

The motors might need to be recalibrated.

 

Thanks Tech! I actually just got the problem fixed! For anyone interested, the problem was that the owner before me had replaced a bad heater core with a 25 dollar universal heater core, which was actually smaller than the correct Volvo core. So the air was just circulating around the outside of the core instead of blowing through it... we fixed the problem by removing the heater core, and cutting pieces of blue board styrophoam insulation (glass transition temp. 203 degrees F, melting point 464 degress F) to fill the excess space inside of the casing. We then covered all of the leaks (from the horrible, homemade cap on the heater core casing) with, you guessed it, duct tape. So far my heater has been blasting hot air and is good to go! I will post here again if the blue board decides to melt, and ruins my day.