I get emails from readers every now and then — but no topic has caused more interest than the 6-pin fan header on my two Inter-Tech server cases, 4U-4416 and 4U-4129-N.
Perhaps for good reason, it allows for the internal 120 mm fans to be PWM controlled. But is completely undocumented! Let’s have a closer look 😃
Table of contents
Our 6-pin header
The header is located right next to the molex power connector for the 3×120 mm internal fans.
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/4u-4129-n-20200501_165655_huf57268482308ba6d55fcacf0469b9a4c_312505_800x0_resize_q80_lanczos.jpg)
A reader, Julien Brunet, tested where the pins went and made a pin-out table.
Fan | Pin row 1 | Pin row 2 |
---|---|---|
Furthest | PWM | Tach |
Center | PWM | Tach |
Closest | PWM | Tach |
The 4-pin fan header
A standard 4-pin fan header provides the fan with 12V, GND, sense and control.
Pin | Wire color | Function |
---|---|---|
1 | Black | GND (0V) |
2 | Yellow | +12V |
3 | Green | Sense/Tach |
4 | Blue | Control/PWM |
Using the 6-pin header
There are two ways that we can use this header to control the internal fans: individually and together.
Individual fans
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/schematics-individually.png)
We can connect the PWM and Tach signals for each fan to a 4-pin fan header on the motherboard, or some other fan controller. This will require three fan headers, and allow us to control and read the speed of each fan individually.
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/unraid-dashboard-fan-speed.png)
Inter-Tech has apparently made a cable for connecting an 8-pin header to four 4-pin fan headers, supporting four internal fans. It is part of their 120 mm fan set — and this is what it looks like:
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/inter-tech-fan-cable_hu5e86c954702473655392f443973f17ae_392725_800x0_resize_q80_lanczos.jpg)
But some jump (DuPont) wires can easily be used instead, just make sure to double check the pin-outs first.
Fans wired together
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/schematics-together.png)
Another way to control the fans, which will only require a single 4-pin fan header, is to connect the PWM signals together.
Let’s have a look at a Noctua NA-SYC1 fan splitter — it takes a single 4-pin fan header and turns it into two. Similar to what we are trying to do.
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/noctua_na-syc1.png)
Looking closely at the Noctua Y-cable, we can see that it splits the PWM signal, but not the Tach signal.
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/20210316_214621_hu92fbfce9917cf39f80de65d7c96593a3_408056_800x0_resize_q80_lanczos.jpg)
This makes sense, as the PWM is a controlling signal going from the motherboard to the fans. But the Tach is the RPM readout going back — so combining the Tach pins makes no sense.
I suspect you need the Tach signal from a single fan to satisfy the motherboard, or whatever fan controller you are using.
Here we can clearly see that one connector is missing pin 3 — the Tach signal.
![](https://blog.cavelab.dev/2021/03/inter-tech-case-fan-header/20210316_214718_hu550d7dcc619ae0f4df9918707adbee60_562040_800x0_resize_q80_lanczos.jpg)
Postface
A special thanks to Julien Brunet for helping me figure this connector out 👍
So with this I feel I have done my part in documenting what this header actually does. I hope you found it useful 😃
Last commit 2021-06-15, with message: publish server case post