Question Connecting older fan to Corsair 4000D and Z790 UD AX ?

[BaaaaL44]

Hi!

I purchased a new rig recently, after retiring my 10 year old configuration. My current setup is:

i5 3600k
RX6800
32GB DDR5 6000 Corsair Vengeance
850W Asus STRIX Gold
Corsair 4000D Airflow
Gigabyte Z790 UD AX
Be Quiet Dark Rock 4

Currently, the case only has the two stock fans installed, and so far, I am not at all dissatisfied with the thermals. GPU remains around 65 even under the highest load, and gaming temps on the CPU are invariably under 70. However, I have thought that installing a second intake fan in the front would be beneficial for cooling. I have extracted one of the HDD bay fans from my old CM Storm Stryker case, and would like to install it to the 4000D Airflow. However, there is a slight problem. Since my config was built by professionals, and the case is pretty crowded, I am unsure how to do it.

When I go into BIOS, Sys Fan1 and Sys Fan2 both show a temperature, but no RPM, whereas CPU OPT shows an RPM and a temperature too. Since Dark Rock 4 only has a single fan (needing no CPU OPT connection) I assume what they did was connect both case fans to CPU OPT using a Y-splitter, so technically my two Sys Fan headers should still be free. The instructions for the motherboard say that all fan headers on the MOBO are 4-pin. However, the conenctor coming from this fan is 3-pin (see attached picture)

20230807-204425 hosted at ImgBB

Image 20230807-204425 hosted in ImgBB

ibb.co

There is also a second wire coming from the fan, which I assume is some sort of LED power connector and which I do not want to connect. The instructions also talk about correct orientation and ground wires, but I do not see one anywhere. Can I just plug this 3 pin connector into the 4-pin MOBO header, and leave the LED wire hanging?

Thank you for your help!

 

[Lutfij]

You can hook up that 3pin fan to any fan header that's on your motherboard;

https://download.gigabyte.com/FileList/Manual/mb_manual_z790-ud-series_e_1201.pdf?v=866a267ffb717dfd6eed73bd829257dd

Your motherboard has 6 fan headers;
SYS_FAN1
SYS_FAN2A
SYS_FAN2B
SYS_FAN3_PUMP
CPU_FAN
CPU_OPT
The header on the motherboard is keyed, so you the 3pins will align with the grooves along the connector for the fan, as stated in this guide.

There is also a second wire coming from the fan
You might want to include more images of the fans and it's connectors that you speak of.

 

[BaaaaL44]

You can hook up that 3pin fan to any fan header that's on your motherboard;

https://download.gigabyte.com/FileList/Manual/mb_manual_z790-ud-series_e_1201.pdf?v=866a267ffb717dfd6eed73bd829257dd

Your motherboard has 6 fan headers;
SYS_FAN1
SYS_FAN2A
SYS_FAN2B
SYS_FAN3_PUMP
CPU_FAN
CPU_OPT
The header on the motherboard is keyed, so you the 3pins will align with the grooves along the connector for the fan, as stated in this guide.

There is also a second wire coming from the fan
You might want to include more images of the fans and it's connectors that you speak of.

Thank you!

Here is what the other wire looks like:

20230808-090925 hosted at ImgBB

Image 20230808-090925 hosted in ImgBB

ibb.co

Also: I can now see that the side of one of the wires going into the 3-pin connector is black, I assume this is what the MOBO instructions mean by the ground wire. Which side of the header should it go?

 

[Paperdoc]

On the 3-hole motor power connector you see two ridges down one side. On the mobo fan headers with pins, you will see a plastic "tongue" sticking up beside Pins 1-3, and Pin 4 is outside that space. The ridges fit around the tongue. There is only ONE way to plug it in, so you cannot get the connection wrong.

The only "trick" to get that older fan working for you is a configuration option in BIOS Setup for the particular mobo fan header you use. See the BIOS Setup manual here

https://download.gigabyte.com/FileList/Manual/mb_manual_intel700series-bios_e.pdf?v=aceb9fb3f69cc73ea6b2fddd6a6f34ed

That fan is called a Voltage Control Mode fan. See p. 6 of the manual. For that particular header set options as follows:
Fan Speed Control Normal
Fan Control Use Temperature Input to Motherboard, not to CPU
Fan / Pump Control Mode to Voltage, not Auto or PWM
Fan / Pump Stop to DISabled so it will NOT stop
Fan / Pump Fail Warning to ENabled so you will get an on-screen warning if it ever does stop
These settings will have the fan's speed controlled automatically according to the temperature measured on the motherboard using the older Voltage Control Mode required by 3-pin fans, and will monitor the fan's speed signal for possible failure.

IF the existing case fans are the more modern 4-pin variety, the configuration options for those on their header should have the Fan / Pump Control Mode to PWM, and others as above.

The fact that the SYS_FAN headers now show temperatures is normal - they always should. NOT showing speeds, though, says there are NO fans currently plugged into them, which leaves one wondering where they are getting their power. Now, you have noticed two SYS_FAN headers, but the manual says there are four - three plain SYS_FAN, and one SYS_FAN3 / PUMP at bottom near the front. This latter can be used for either function, and its configuration options include one to specify whether it is used for a fan or a pump. SYS_FAN1 is at top near the rear; SYS_FAN2A and 2B are at the front near the top. Perhaps the other case fans are connected to one or two of these. IF the speeds of those case fans do change with workload, they must be connected to some header that does that job. IF they are connected simply to a PSU power output connector, then they will always run full speed. IF they are connected to CPU_OPT as you suspect, that is wrong. That header is controlled according to the temperature measured inside the CPU chip, whereas it should be controlled (using a SYS_FAN header) by the temp on the motherboard.

 

[BaaaaL44]

On the 3-hole motor power connector you see two ridges down one side. On the mobo fan headers with pins, you will see a plastic "tongue" sticking up beside Pins 1-3, and Pin 4 is outside that space. The ridges fit around the tongue. There is only ONE way to plug it in, so you cannot get the connection wrong.

The only "trick" to get that older fan working for you is a configuration option in BIOS Setup for the particular mobo fan header you use. See the BIOS Setup manual here

https://download.gigabyte.com/FileList/Manual/mb_manual_intel700series-bios_e.pdf?v=aceb9fb3f69cc73ea6b2fddd6a6f34ed

That fan is called a Voltage Control Mode fan. See p. 6 of the manual. For that particular header set options as follows:
Fan Speed Control Normal
Fan Control Use Temperature Input to Motherboard, not to CPU
Fan / Pump Control Mode to Voltage, not Auto or PWM
Fan / Pump Stop to DISabled so it will NOT stop
Fan / Pump Fail Warning to ENabled so you will get an on-screen warning if it ever does stop
These settings will have the fan's speed controlled automatically according to the temperature measured on the motherboard using the older Voltage Control Mode required by 3-pin fans, and will monitor the fan's speed signal for possible failure.

IF the existing case fans are the more modern 4-pin variety, the configuration options for those on their header should have the Fan / Pump Control Mode to PWM, and others as above.

The fact that the SYS_FAN headers now show temperatures is normal - they always should. NOT showing speeds, though, says there are NO fans currently plugged into them, which leaves one wondering where they are getting their power. Now, you have noticed two SYS_FAN headers, but the manual says there are four - three plain SYS_FAN, and one SYS_FAN3 / PUMP at bottom near the front. This latter can be used for either function, and its configuration options include one to specify whether it is used for a fan or a pump. SYS_FAN1 is at top near the rear; SYS_FAN2A and 2B are at the front near the top. Perhaps the other case fans are connected to one or two of these. IF the speeds of those case fans do change with workload, they must be connected to some header that does that job. IF they are connected simply to a PSU power output connector, then they will always run full speed. IF they are connected to CPU_OPT as you suspect, that is wrong. That header is controlled according to the temperature measured inside the CPU chip, whereas it should be controlled (using a SYS_FAN header) by the temp on the motherboard.

Thanks! I'll take a look when I get home to make sure, but when you say it's "wrong" to plug them into the CPU_OPT header, you mean "wrong" as in "going to damage your computer" or "wrong" as in "technically wrong, but if temps are okay, it's fine"? This rig cost 3 months of payment where I live, and temps are fine, so I wouldn't really want to mess around unless it's necessary.

 

[Paperdoc]

"Wrong" only becasue the basis for controlling the speed of a fan on that header is the wrong temperature sensor, although the CPU internal temperature is related to the overall heat generation by motherboard components. Doing it this "wrong" way will NOT do any damage to anything, really.

As you look, try to find where the two existing case fans are plugged in. ALSO consider: do their speeds actually change as your system workload changes? IF the only run full speed all the time, then they are NOT under automatic control by any mobo header. But if they DO change speeds, they must be plugged into something (probably a mobo header) that does that control.

 

[BaaaaL44]

"Wrong" only becasue the basis for controlling the speed of a fan on that header is the wrong temperature sensor, although the CPU internal temperature is related to the overall heat generation by motherboard components. Doing it this "wrong" way will NOT do any damage to anything, really.

As you look, try to find where the two existing case fans are plugged in. ALSO consider: do their speeds actually change as your system workload changes? IF the only run full speed all the time, then they are NOT under automatic control by any mobo header. But if they DO change speeds, they must be plugged into something (probably a mobo header) that does that control.

I just checked, and none of the SYS_FAN headers are occupied, neither the one in the upper left, nor the two on the right side. The CPU_OPT header is occupied, however. Unfortunately, I cannot discern the Y-splitter they used to plug both case fans, because the cables are all bundled and tied together on the opposite side of the MOBO, but I assume that's what is going on. If I understand correctly, as long as the temps are okay, I can leave it like this, correct? I would really prefer not to mess up the cable routing and potentially mess something up in the process.

Thanks again for the great help!

 

[Paperdoc]

Yes, there is no compelling need to change that. For simplicity, leave it alone. You're welcome.

 

[BaaaaL44]

Yes, there is no compelling need to change that. For simplicity, leave it alone. You're welcome.

Thanks!

Just one more question if you don't mind: I am now considering installing a second intake fan in the front (Be Quiet Silent Wings 4) because plugging in a single connector is something I probably would manage. It would be fine to plug that one into one of the SYS_FAN headers to allow it to be controlled by MOBO temps, correct?

 

[Paperdoc]

Correct, that is the right way.

 

[BaaaaL44]

Correct, that is the right way.

Just to update, I managed to install a Be Quiet Silent Wings 4 120mm front intake fan, and it dropped my CPU temps fairly significantly (5 to 10 degrees celsius across the board, depending on load). Installation was definitely simpler than I had made it out to be, so thank you again for the educational answers. Also: I found a setting in my BIOS that allows me to slave any fan header on the mobo to either the CPU or the system sensors, so I can basically run my two fans plugged into CPU_OPT based on mobo temps.

 

[Paperdoc]

Good find. Congrats on getting this done.