I have a VisionTek Radeon HD 4870 card that, in recent months, has begun to overheat while at idle, requiring me to manually set the GPU fan speed at 70% or higher (I had thought that the normal ATI Catalyst Control software had a function to automatically speed up/down the fan to prevent overheating, but if it does the feature isn't working).
Any ideas on what might be causing my card to overheat while it's doing nothing?
The GPU will get up to 80C when it will get unstable enough to crash the system.
Setting the fan to a high speed (like the 70% speed I now keep it at) will keep the temperature around 44C.
I've tried spraying out the card's grill and fan with canned air; to clean any deeper I would have to disassemble the card's plastic case, and I'm not confident enough in my ability to not break electronics to do that.
Here's a (stock) photo of the card, so you can see what I'm talking about
the plastic shroud should come off easily enough, just some screws... but dont loosen the screws on the gpu back bracket or the heatsink itself will come off and then it'll need some more tinkering, reapplying paste and all that...