I just got a used gtx 560 ti hawk on ebay. I used nvidia 280.26 and msi afterburn, but when I set the fan speed to 100%, it doesn't sound anything; i saw the fan rpm doesn't increase at all. I also tried downgrade to another driver, but the problem still persist. is this hardware or software issue? the card hit 100 when full load within 1 minute cause me can't do anything with it.