Fan stops spining during games. (POWERCOLOR ATI PCS+ HD4870)

Hello everyone. I have an issue about my video card. 2 weeks ago my computer suddenly crashed when i was playing l4d. At first i thought my card was overheating and i was right. Then i realized it is overheating because of it's fan. But the weird thing is it stops spinning in games. When i return to windows it starts spining again. It was set to auto in CCC v9.6. Now it is set to 65% manual speed. But eventually it is crashing again after 1 hours of play. Does anyone have any idea about this problem? Thank you.

The fan control should be all on the graphics card. That means the graphics card is the problem.

So either you need to RTM it if still under warranty or void your warranty and add a custom cooling solution that doesn't rely on fan control from your graphics board.

The only other thing I can think of is that the firmware could be reflashed as maybe it's not working properly. If I knew what card you had maybe I could Google for more info.