The Third fan of my GPU SAPPHIRE R9 290 stops spinning immediately after i turn on the pc is this means that my card is defective or could it be something else like the power source
It might be that the bearings for that fan have crapped out and need a bit more power to get it started spinning, are you hearing any strange noises from the fan when it starts spinning? I'd try replacing that fan and seeing if that solves the problem.
I don't hear any strange noises from the fan if it's spinning and if I turn the fan by my self than it spins flexible without any struggling noise.
If I want to try to replace the fan do you know where I can buy a new one.
Sapphire has incorporated a Fan Control in its GPU cards called : Intelligent Fan Control II
Intelligent fan control allows one or more fans to be stopped for lower noise when the card is under light load and automaticaly restarted when the card temperature rises
Most likely the third fan is turned off until Intelligent Fan Control II determines it is needed to run. Unless, as stated earlier, the third fan is making unusual noises like rasping or grinding. If not, and the all three fans start normally when the computer boots up and then the third stops, it probably is being controlled by Sapphire's Intelligent Fan Control II.
That could be a thing too, I assumed since it's a 290 that he likely had the card for a while and was familiar with the way it normally operated...... but it's possible he bought the card used and he's just not used to it yet.
I agree, that is why it is important for Users to post as much of their computer setup as possible. Otherwise, other Users like yourself and I will give advice based on what the OPS posted.
It is very important to know if the GPU card is used or new. If used, you have no idea what was done to the GPU card prior to being sold such as modifying the vBIOS or even being a fake GPU card.