Volvo: Defrost, automatic climate control, v70 xc

Question
I have a 98 V70 XC. It has 153,000 miles on it I love it. Recently the defrost does not work well. I usually keep it on automatic climate control. Even when I put it on defrost it still doesn't work well. I have never had this problem before.

Answer
Julie,
Is it not working well because of the vents not positioning to the windshield or does the blower moter stop working? Is the heat hot enough on the heat setting? Are you using it in an area where there is fog or frost on the wondshield? What temp ranges are you experiencing problems in? The A/C compressor comes on with defrost if the temp is above 32 degrees. Does that happen?
You did not state for what reason the defrost fails to work.