Question CPU fan outlet not working??

[tijuanagenius]

When my heatsink fan is plugged into the designated 4 pin CPU fan outlet on my motherboard, it will often start off super slow to point where it's only "twitching"
The fan sits idle to the point where my PC crashes from overheating.
I've turned on and off Cool & Quiet, and reset my motherboard's cooling settings multiple times
I've tried the GIGABYTE fan control app, and also third party fan control apps
I mean, they "worked" but were very impractical as they don't take effect until the app starts and most of the time they don't start at all and my PC ends up crashing from overheating anyway

I've tried different heatsinks, fans, and thermal paste. All behave the same.

For the last few months I've had my CPU fan plugged into a case outlet and a case fan plugged into the CPU outlet
The case fan works from the CPU socket, it doesn't do the twitchy thing. I assume this is because its only 3 pin and doesn't get the variable speed data from the 4th pin

This workaround is keeping my PC running, I'm just wondering if anyone had any ideas what's causing this.

Thanks!

Motherboard is GIGABYTE GA-970A-UD3P (rev. 1.0), and it does have the lastest BIOS installed
CPU is AMD FX(tm)-6300 Six-Core Processor

 

[Paperdoc]

I can suggest three possible causes and remedies you can try. But first, a bit of info on the fan headers your mobo has.

The CPU_FAN header is really the proper one to use for the CPU fan. It is guided by the temperature sensor inside the CPU chip, whereas the SYS_FAN1 header is guided by a different sensor on the mobo. Further, the CPU_FAN header monitors its fan's speed signal closely and should send out a warning to you if it fails. If it detects fan failure it might even take drastic action and shut down the entire system to prevent CPU damage by overheating. The SYS_FAN1 header is the ONLY case fan header able to control fan speeds. As a matter of fact, it does this using the older Voltage Control Mode even though it is a 4-pin header, so it can control either a 3-pin or a 4-pin fan. Both the SYS_FAN2 and PWR_FAN header can do NOT control at all, so any fan plugged into one of these will always run full speed.

1. It is just possible that the fan's contacts in the connector to the CPU_FAN header were poor and it was getting bad signals from that header, even though the fan is OK. To test for this, change the fan connections back to original - CPU fan to CPU_FAN header, case fan to SYS_FAN1. When doing this, plug the CPU fan into its header, unplug, re-plug etc. a couple of times. IF there was a dirty contact there, this will scrub it clean and the fan will work properly. Now start up and observe whether the fan is working properly, or is still misbehaving. If it's still bad, proceed.

2.See your mobo manual, p. 40, under "CPU Fan Speed Control". One option is to use Manual control, and set a value for the "Slope PWM" item. IF you have it set this way, that Slope PWM value may be too low, causing the fan to get signals to run too slow. If that's the case, set it higher OR change it to "Normal" control so the mobo uses its own pre-set values. On the other hand, IF you do NOT have it set this way (if you have it set to "Normal" control), you can try to force a higher fan speed by changing to the Manual option and setting the Slope PWM value higher. Then experiment a bit and see what setting makes the fan run smoothly under all operating conditions, (especially when cold and first started up).


3. The fan may be failing (worn bearings) so that it runs much slower than it should. Currently you have it plugged into some mobo header (not specified) and it works. IF it is in the SYS_FAN1 header it may be receiving from that header a voltage signal sufficient to keep it going, but different from what it was getting from the CPU_FAN header. IF it is on one of the other two headers, it will be receiving a full 12 VDC supply and running at full speed all the time. This only proves the fan is not dead, but it still may have bad bearings causing it to run slower than normal. So, if ideas 1 or 2 have not fixed this, your best option will be to replace that fan.