CPU Fan Not Spinng - CPU Header Low Voltage?

[techbob]

I have an old AM3 system - AMD Phenom II X4 955 and Gigabyte MB. Not my primary rig, This system is used for light stuff and a single virtual machine. OS is Linux Mint.

It recently overheated and noticed the CPU fan wasn't spinning. When I give it a flick with my finger it spins up. I assumed that it was a bad fan but when connected to a 3 pin system fan header, it spins just fine, and fast. I guess the big Xigmatek cooler was keeping it alive.

-Is it correct to assume that the CPU header wasn't suppling enough voltage?
-Could it be anything other than a the motherboard dying - such as PSU?
-On board GPU so not much power used
-Is it OK to use the system fan header indfinitely to power the CPU fan indefinitely? The Antec case is very quiet so sound isn't an issue and it starts up just fine.
-I moved all critical stuff to other machines and all backed up. So if it goes belly up no big deal,

Going forward, since processing power is adequate, would it make sense to get a new AM3+ MB and a low end PCI-E GPU and re-use the memory, PSU and other stuff? I really need to build a higher end new system but not ready for that yet.

Thanks!

 

[Spartacus]

As fans get older, they don't spin as easily as when they were new.
So when the mobo puts out a low voltage for low RPM, it's not enough to spin up the fan any more.

If you don't mind the noise, then just run the fan at full speed.

In my systems, if I'm going to run the fan at full speed, I connect it directly to the PSU and I don't
use the mobo fan headers. It prevents stressing the mobo with the current draw from the fan.

You can also use one of those noise reducing adapters if you have any laying around. You can
still connect it to the PSU but the adapter with the resistor in it will drop the power & noise.

.

 

[techbob]

As fans get older, they don't spin as easily as when they were new.
So when the mobo puts out a low voltage for low RPM, it's not enough to spin up the fan any more.

If you don't mind the noise, then just run the fan at full speed.

In my systems, if I'm going to run the fan at full speed, I connect it directly to the PSU and I don't
use the mobo fan headers. It prevents stressing the mobo with the current draw from the fan.

You can also use one of those noise reducing adapters if you have any laying around. You can
still connect it to the PSU but the adapter with the resistor in it will drop the power & noise.

.

Thanks! The cooler is a big XIGMATEK, and to replace the CPU fan the MB has to be removed. The rubber fan mounts that attach to the cooler fins makes things complicated. I'll need to get a 4 pin adaptor to connect to molex, only have 3 pin to molex.