If the lights are blinking as Klaus describes, she can buy a can of compressed air at Wal-mart and blow through the front little grill like cover of the temp sensor to clean out the dust. If that works, you can save the time and trouble of removing the sensor. I didn't have as good of instructions as Klaus has given here and was having trouble trying to get to the sensor when I read a post about this possible fix. It took care of the problem and has continued to function well for several months now since blowing it out. (I suggest not trying to poke the tube that comes with the can of air through the little grill covering - it is very fragile and will break easily - just put it up against the grill and blow the air through it.)

Good luck, Calvin (2000 V70, 88K)