My ati sapphire x1950 pro fan is really messed up. it sometimes chooses to work, maybe 1/20 times when i need it, the other times it just twitches, it'll move 2mm forward and then 2mm back not spinning at all.
Without the fan my idle temp is around 90 degrees Celsius. When I do a render test it will go over 130 degrees , catalyst control center isn't even able to show 130, it max's at 125.
After a couple minutes the video card gives up and the screen goes black, this happens all the time when i have a game running and its really annoying. All the video card program i have say the fan is spinning 100%, but its not.
Then it may be bad and it is in your interest to replace the cooler then if the fan feels like it is off balance or bringing when you try to spin it. The VF900 is a good fit while there are cheaper coolers around so do a little research there and you will find just the right one for you. I own only zalman gpu coolers so I only recommend them.