Fans run at full speed with PWM Fan Hub

bcmthhd · Jun 17, 2015

Hi guys,

I currently have 5 case fans (3 Noctua, 2 stock Corsair). Previously, I used 3 Y cables to connect 4 fans directly to the motherboard which has only 1 socket. And I can control those Noctua just fine. Then I decide to have SilverStone Technology All Black 1-to-8 PWM Fan Hub (CPF04), now all my fans are running at full speed. And to be honest, it sounds pretty loud.
So, where do you guys think the problem is?

Thank you so much!

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor
CPU Cooler: Noctua NH-L9i 57.5 CFM CPU Cooler
Motherboard: ASRock Z97M-ITX/AC Mini ITX LGA1150 Motherboard
Memory: Crucial Ballistix Tactical 8GB (2 x 4GB) DDR3-1600 Memory
Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive
Video Card: Asus GeForce GTX 970 4GB STRIX Video Card
Case: Corsair 250D Mini ITX Tower Case
Power Supply: Corsair CSM 550W 80+ Gold Certified Semi-Modular ATX Power Supply
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer
Case Fan: Noctua NF-S12A PWM 120mm Fan
Case Fan: Noctua NF-A8 PWM 32.7 CFM 80mm Fan
Case Fan: Noctua NF-A8 PWM 32.7 CFM 80mm Fan
Monitor: Asus VG248QE 144Hz 24.0" Monitor

Paperdoc · Jun 17, 2015

The hub has two cables - one for power from the PSU, one with 4 wires to plug into the mobo 4-pin SYS_FAN port. Is that latter cable plugged into the SYS_FAN port? Your problem description indicates that the hub may not be receiving the PWM signal from Pin #4 of the port. On a PWM system, LACKING a PWM signal makes the fan run full speed all the time.

<Answer deselected at thread originator's request>

bcmthhd · Jun 17, 2015

Paperdoc :

I just checked the cable. There are only 2 pins. I'm not sure that the way it should be. I can still see the fan speed data on BIOS though.

ryQePjfAsS4ZP9i4-MAenlwGKU7Nn-1JmYnfMHcZvu9sFZYtDdtSepLuSYG0sJWrsea_Rf_04V8fGDk=w1896-h859

Update: That how it should be. I just looked it up on SilverStone website. Is it because I'm not using same brand?

Paperdoc · Jun 18, 2015

That is correct. If you have plugged this into the mobo's 4-pin SYS_FAN port it should work just fine. Because of the groove on one side that mates with a tongue on the mobo male port, it only fits on one way. On the 4-pin connector you show in your picture, the two pins missing wires are #1 - Ground, and #2 - +12VDC supply. The hub does NOT need either of these. The pins with wires are: #3 - Speed Pulse signals from (one) fan motor back to the mobo, and #4 - PWM signal. The speed signal is why you ARE getting speed info from your mobo - it is receiving these pulses and counting them normally. The hub sends back to the mobo only ONE fan's signal - the one from hub port #1, the one marked off from three others on one side of the hub - because the BIOS's counter can only handle a train of pulses from one fan. The hub also needs the PWM signal it is getting through Pin #4 so it can share that around to all its 4-pin fans.

So we are left with a few possibilities. One is the configuration of the SYS_FAN port in BIOS Setup. SOME mobos allow you to set the 4-pin fan port mode to either 4-pin or 3-pin mode. Check how yours is set in BIOS - it should be 4-pin (PWM) mode. If it is in 3-pin or Voltage Control Mode, the port is not using the PWM signal (which the hub needs) and is trying to control fan speed by altering the voltage on Pin #2, which your hub does not even receive or use.

Check also in BIOS to be sure your mobo SYS_FAN port is set to Automatic control, and not to some fixed speed that is specified there.

The last possibility, of course, is that the hub could be faulty.

bcmthhd · Jun 18, 2015

Paperdoc :

That is correct. If you have plugged this into the mobo's 4-pin SYS_FAN port it should work just fine. Because of the groove on one side that mates with a tongue on the mobo male port, it only fits on one way. On the 4-pin connector you show in your picture, the two pins missing wires are #1 - Ground, and #2 - +12VDC supply. The hub does NOT need either of these. The pins with wires are: #3 - Speed Pulse signals from (one) fan motor back to the mobo, and #4 - PWM signal. The speed signal is why you ARE getting speed info from your mobo - it is receiving these pulses and counting them normally. The hub sends back to the mobo only ONE fan's signal - the one from hub port #1, the one marked off from three others on one side of the hub - because the BIOS's counter can only handle a train of pulses from one fan. The hub also needs the PWM signal it is getting through Pin #4 so it can share that around to all its 4-pin fans.

So we are left with a few possibilities. One is the configuration of the SYS_FAN port in BIOS Setup. SOME mobos allow you to set the 4-pin fan port mode to either 4-pin or 3-pin mode. Check how yours is set in BIOS - it should be 4-pin (PWM) mode. If it is in 3-pin or Voltage Control Mode, the port is not using the PWM signal (which the hub needs) and is trying to control fan speed by altering the voltage on Pin #2, which your hub does not even receive or use.

Check also in BIOS to be sure your mobo SYS_FAN port is set to Automatic control, and not to some fixed speed that is specified there.

The last possibility, of course, is that the hub could be faulty.

I just removed the hub and used those Y cables. It works fine. I guess it's the hub's problem. Last questions, do you think I should get another hub or just stick with Y cables? Is it okay to run 5 fans on 1 header?

Thank you so much!

Paperdoc · Jun 18, 2015

I suggest get another hub, specifically one for 4-pin (PWM) fans as you have. Generally I do not think that one mobo fan port can handle the short heavy start-up current for more than 2 fans. A 4-pin hub solves this problem very well. Maybe check whether the one you have can be replaced under warranty.

bcmthhd · Jun 28, 2015

Paperdoc :

I found the problem. I bought a Swiftech fan hub this time. Nothing changes when I use the chassis port. But they recommend to use the CPU_Fan port, so I give it a try. Everything turns out to be just fine. Now, I'm using chassis port for CPU cooler and vice versa.

PHgraphicsguy · Jul 29, 2015

bcmthhd :

I had the same concern before but I used the CPU fan header for my push pull method cooling my CPU using a PWM fan hub and it works like a charm even on the other sys fan header i added a pwm fan hub connected to 3 PWM Fans and all are running under PWM BIOS setup. So far so good. cheers!

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