GPU Fan Kinda Stopped Working

shakenbreak · April 13, 2016

So today I tore down my computer to clean out all the dust, and since I have really old parts that likely don't have warranties anymore I took my graphics card apart too. Upon putting it back together and booting up the fan only spun a little then stopped. I thought that was weird so I opened up MSI Afterburner and set the fan speeds at 30, 40, 50, 60, 70, 80, 90, and 100 percent. The fan only spins at 90 and 100 percent. If I get the fan to spin I can manually put it down to 87 percent and if I go to 86 it stops working all together. I checked all the wires on the fan and they look fine, and the connection to the pcb of the card is good as well. Any ideas what could be wrong with it?

Naeaes · April 13, 2016

Spinning up takes more energy that maintaining a high speed. That's why going to full and then ramping down works. That's also a big part of the reason why all fans spin at max for a few seconds when you turn on a computer.

The fan has 2 wires, right? That means the controller doesn't actually know how fast it's spinning or even if it's spinning or not. It just pumps in a percentage of the maximum voltage and hopes for the best. It can use the data from the temperature sensor to work out if more or less voltage is needed.

Which leads to a problem. Say you have an old fan with a worn-out bearing. It runs if it gets ample voltage but the voltage required has shifted up from what it used to be. And the controller has no idea that this is going on. It would give it more juice (up to a certain safe level) if it only knew that that's what it needs. You can keep the voltage high enough to keep the fan spinning for now, but it's already on it's way to the fan heaven. The issue will only get worse over time.

The fact that the issue presents itself just when you cleaned it is all just by happenstance, I bet. You could try re-lubricating the bearing. Dust has all the properties needed to dry up a bearing over time. But if the bearing is broken, it won't help. All in all, your best bet would be to replace the fan or considering the difficulty of finding a compatible spare part, the whole cooler.

Same issues plague 3-wire fans too. But the difference is that those fans report their actual speed back to the controller. Those controllers can tell the speed in RPM instead of % which is why I'm assuming yours is 2-wire. Also that's more common.

shakenbreak · April 13, 2016

1 hour ago, Naeaes said:

Spinning up takes more energy that maintaining a high speed. That's why going to full and then ramping down works. That's also a big part of the reason why all fans spin at max for a few seconds when you turn on a computer.

The fan has 2 wires, right? That means the controller doesn't actually know how fast it's spinning or even if it's spinning or not. It just pumps in a percentage of the maximum voltage and hopes for the best. It can use the data from the temperature sensor to work out if more or less voltage is needed.

Which leads to a problem. Say you have an old fan with a worn-out bearing. It runs if it gets ample voltage but the voltage required has shifted up from what it used to be. And the controller has no idea that this is going on. It would give it more juice (up to a certain safe level) if it only knew that that's what it needs. You can keep the voltage high enough to keep the fan spinning for now, but it's already on it's way to the fan heaven. The issue will only get worse over time.

The fact that the issue presents itself just when you cleaned it is all just by happenstance, I bet. You could try re-lubricating the bearing. Dust has all the properties needed to dry up a bearing over time. But if the bearing is broken, it won't help. All in all, your best bet would be to replace the fan or considering the difficulty of finding a compatible spare part, the whole cooler.

Same issues plague 3-wire fans too. But the difference is that those fans report their actual speed back to the controller. Those controllers can tell the speed in RPM instead of % which is why I'm assuming yours is 2-wire. Also that's more common.

It's actually a 4-wire fan. I'll have to do some looking on ebay or something to see if there's any replacement heatsinks or just fans for it.