CPU fan not spinning, No Post, beeps or image, all other fans spinning normally

[joelayton]

Hi, its my first build and I have encoutnered a problem. On first boot all fans come on normally except for the CPU heatsink fan that spins for only a second or so then stops, it then fails to post or display any image on the monitor. I have read all stickies and tried the simple steps. Have swapped out PSU for a test with no change.

Any help would be greatly appreciated.

 

[joelayton]

My specs are as follows:

MOBO: Gigabyte 970A-DS3P AMD 970 Motherboard
CPU: AMD FX-8350 BLACK EDITION 4.0 GHZ, 8 CORE
GRAPHICS CARD: GIGABYTE GTX 750 TI
HDD: SEAGATE 500GB 7200RPM
MEMORY: 2X4GB CORSAIR VENGEANCE DDR3 1600
PSU: COOLERMASTER 500W PSU
CASE: BITFENIX NEOS WINDOWED CASE

 

[nexusparties]

Check and see if the CPU fan is plugged in it should be around the processors area should be a little white tab just plug the fan back in and it should run if it doesn't start up after that than the fan most likely doesn't work anymore and you should replace it, also avoid running your computer without a fan for a good amount of time you'll burn out the processor.

 

[joelayton]

Check and see if the CPU fan is plugged in it should be around the processors area should be a little white tab just plug the fan back in and it should run if it doesn't start up after that than the fan most likely doesn't work anymore and you should replace it, also avoid running your computer without a fan for a good amount of time you'll burn out the processor.

I have tried unplugging and replugging the fan several times but to no avail. Is a faulty fan liely to be the problem? It seems to spin absolutely fine for a few seconds then stops so it doesnt appear to be a problem with the motor or the like. Starting to think it could be a mobo problem

 

[nexusparties]

Check and see if the CPU fan is plugged in it should be around the processors area should be a little white tab just plug the fan back in and it should run if it doesn't start up after that than the fan most likely doesn't work anymore and you should replace it, also avoid running your computer without a fan for a good amount of time you'll burn out the processor.

I have tried unplugging and replugging the fan several times but to no avail. Is a faulty fan liely to be the problem? It seems to spin absolutely fine for a few seconds then stops so it doesnt appear to be a problem with the motor or the like. Starting to think it could be a mobo problem

It couldn't be a mobo problem because everything else is working fine, if all the other fans are spinning then it isn't the mobo. If you have another computer laying around try using the fan from that computer and if it works it's the fan, if not then there may be something else wrong elsewhere.

 

[Goldengoose]

Sounds like your BIOS is outdated.

I had the same issue. Bought a new machine and got the Ivy Bridge only a few weeks after it had come out. The MB stated that it supported ivy Bridge but obv hadn't been updated or was old stock due to how fresh and new the CPU was. I had no old CPU's i could update with so took it some shop to have the BIOS updated.

Are you able to put an older CPU in to try it?

 

[joelayton]

Sounds like your BIOS is outdated.

I had the same issue. Bought a new machine and got the Ivy Bridge only a few weeks after it had come out. The MB stated that it supported ivy Bridge but obv hadn't been updated or was old stock due to how fresh and new the CPU was. I had no old CPU's i could update with so took it some shop to have the BIOS updated.

Are you able to put an older CPU in to try it?

that might just work, the mobo was an ex-display model so could potentially have been sat on a shelf and not updated i guess? did the shop charge much to update it ?

 

[Paperdoc]

I, too, am more inclined to suspect the mobo's control of the fan, and not the fan itself. When you first turn on power, all fans controlled by mobo ports will start up at full speed. After a few seconds when the BIOS completes the first part of its POST, it will get around to actually initiating automatic control of the fans and slow them down because all the components are still cool. Later it will speed them up again as things warm up. It appears that, in this process, the automatic control of the CPU fan is shutting it off completely. And MAYBE that is related to how the BIOS recognizes and deals with the CPU and its built-in temperature sensor. So a BIOS update may well be the solution.

There are three other things I suggest you check to confirm your information.

1. All such fans operate at 12 VDC or less. That is the voltage from an automobile battery. So you could remove the CPU cooler fan from your case (or, bring a 12 V battery to your computer) and connect the fan to that supply. Disconnect the fan from the mobo port. On the fan's connector, the contacts are Pin #1 for negative, and Pin #2 for positive. If it's a 3-pin fan, the wires are Black and Red. If it's a 4-pin fan, they will be Black and Yellow. If the fan starts immediately and keeps running smoothly, you know it is OK.

2. Another more unlikely cause is a poor connection at the mobo port. Many modern mobos have a special protection system for the CPU cooler. They monitor the speed of the CPU cooling fan. That speed is a pulse signal generated inside the fan motor and sent back to the mobo on Pin #3. If the mobo (once it is actually doing its fan control process) senses that the fan is NOT turning (that is, it gets no signal from the fan on port Pin #3) it will shut down the whole system immediately. This is to prevent overheating of the CPU with no cooling. Note that the system for this fan does not even wait for the measured temperature inside the CPU to go high - it pre-supposes that that disaster will be inevitable if there is no fan cooling. So, check carefully the connection of CPU fan to mobo port.

3. All of this presumes something: that you actually do have the CPU cooling fan plugged into the mobo port marked for CPU_FAN, and NOT somewhere else. Is that true?

 

[Goldengoose]

Sounds like your BIOS is outdated.

I had the same issue. Bought a new machine and got the Ivy Bridge only a few weeks after it had come out. The MB stated that it supported ivy Bridge but obv hadn't been updated or was old stock due to how fresh and new the CPU was. I had no old CPU's i could update with so took it some shop to have the BIOS updated.

Are you able to put an older CPU in to try it?

that might just work, the mobo was an ex-display model so could potentially have been sat on a shelf and not updated i guess? did the shop charge much to update it ?

I think it was £15. Make sure you go to a small PC independent shop/repair shop and not PC world or something similar (big chain company).