Question Case fans starting upon boot, then stopping, then sequentially starting

[WEYxAYYZ]

Hi,

I'm having an issue with my case fans.

I have just had built a PC with the following:

• Fractal Designs Meshify Lite RGB case which comes with 4 case fans
• Gigabyte b760m ds3h ax ddr5 motherboard (https://download.gigabyte.com/FileL...ries_e.pdf?v=25a71a17f8dd4e1de0051392873fcd4d)
• Fractal Design s36 rgb liquid cpu cooler

Connection wise, the 4 case fans are daisy chained without a splitter into sys_fan3 on the mobo. The AIO is plugged into cpu_fan. The top 3 fans connected to the AIO are plugged into sys_fan2 via a splitter.

The case fans and top 3 fans from the cooler are daisy chained together for rgb.

All rgb on the fans works fine with the built in case controller. The rgb on the AIO doesn't work, remains white when connected to the D_LED on the mobo and isn't recognized by any software but can live with this.

The issue is, when I initially boot up the PC, all 4 case fans spin for around 5 seconds. They then come to a complete stop. And over the next 5-10 minutes they sequentially turn on, the front lower fan turns on first, followed by the front upper fan, then the middle and rear fans at the same time. Once they're all back on, they remain on.

I can manually start the case fans using fan control software, and can also vary the rpm of the fans using this tool too.

Any thoughts on why the fans could be behaving this way?

 

[Paperdoc]

For this AIO system the design intends that the PUMP be connected to the CPU_FAN header AND that the header be configured a particular way. Likewise, where you connect the RAD FAN MOTORS and how that header is configured is important. In this design, the pump is supposed to operate at full speed all the time, and the RAD FANS' speeds are controlled by the mobo guided by the temperature sensor inside the CPU chip to keep that chip's temperature on target. To achieve these things, configure this way. See the BIOS Setup manual here on pages 6 and 7.

https://download.gigabyte.com/FileL...bios_e.pdf?v=aceb9fb3f69cc73ea6b2fddd6a6f34ed

1. PUMP cable to CPU_FAN header. In BIOS Setup configure this header:

Fan Speed Control to Normal. This uses the pre-programmed settings to adjust your AIO system for workload changes.
Fan Control Use Temperature Input to CPU IF you have a choice - often the CPU_FAN header does not allow any other setting
FAN/PUMP Control Mode to PWM (NOT to Auto or Voltage) - this uses a quirk of the 4-pin fan system design so that your pump can only run full speed all the time.
FAN/PUMP Stop DISabled so it can NOT stop ever
FAN/PUMP Fail Warning ENabled so you do get a prominent warning if ever the pump stops

2. SYS_FAN2 header where you have connected all three RAD FANS via a Splitter
This will be very similar but with important differences
Fan Speed Control to Normal. This uses the pre-programmed settings to adjust your AIO system fans speeds for workload changes.
Fan Control Use Temperature Input to CPU - THIS is IMPORTANT - the rad fans MUST be guided by the temp sensor inside the CPU chip
FAN/PUMP Control Mode to PWM (NOT to Auto or Voltage) - this is the correct way to control the speed of 4-pin PWM fans
FAN/PUMP Stop DISabled so they can NOT stop ever
FAN/PUMP Fail Warning ENabled so you do get a prominent warning if ever a particular fan fails (see next)

Any fan header can deal with the speed signal returned to it from only ONE fan. So when you connect three fans to the SYS_FAN2 header via a Splitter, the Splitter sends back to that header the speed of only ONE fan. Specifically (look very closely at the three output connectors of the Splitter) it sends back the signal from the output connector that has ALL 4 pins. So only that one fan can be monitored for failure. From time to time YOU should check to ensure that all 3 rad fans are working.

So, set your stuff up this way and observe the rad fans. They should never stop.

Onward to your four case ventilation fans on SYS_FAN3. Configure that header just like the SYS_FAN2 header EXCEPT for one point.
Fan Control Use Temperature Input to MOTHERBOARD - THIS is IMPORTANT - the case vent fans MUST be guided by the temp sensor on the mobo, not by the one in the CPU chip.

So, why do those case fans act oddly? That MAY be from an incorrect configuration setting which may be corrected from doing those things. IF the header was set to use Voltage Control Mode it may have sent out signals to run so slow that they stall. IF you set Fan Speed Control to a fixed slow speed (like "Quiet") the same might be happening. Another possibility is that the "Normal" "fan curve" actually is not right and tells those fans to run too slow at the lowest temperatures. If that is the case, you can change this by using instead the "Manual" option for Fan Speed Control. When you choose that you can use your cursor to drag the points on the "fan curve" shown on your screen so that, at the lowest one or two temperatures, the minimum speed is a bit faster that originally set and you can ensure those fans never stall. This may take a few tries to find the right minimum speed.

Note that the use of the Manual setting and adjusted fan curve process also can be used for the SYS_FAN2 header where the rad fans are connected IF you need to.