no rpm control PWM fan with 2A 4pin header

t-nought

Commendable
Feb 8, 2017
3
0
1,510
Asrock x470 master sli/ac motherboard + Delta electronics 120mm PWM fan.

I've tried connecting this fan to the 2A CPU2/waterpump 4-pin header, and I have no rpm control. The fan is not detected with HWINFO64, and has no RPM reading in the BIOS (reads 'NA'). However, in the bios I am able to change some things as follows:

PWM mode: runs 100% all of the time
DC mode: fan stops
AUTO mode: fan revs up, then stops, revs up, then stops, etc.

The fan is not responsive to other settings like quiet, standard, etc Other 4pin fans I have work fine with this header.


In the past I've never had to trouble shoot a new fan, so I'm not sure where to start troubleshooting from here. Thank you.
 
Solution
Yes, the photos of the fan show it uses the other common colour coding scheme: Black, Red, Yellow, Blue. BUT there is one oddity there. On a normal 4-pin fan, Yellow is the Speed Pulse signal being fed back on Pin #3, and Blue is the PWM signal supplied on Pin #4 from the mobo. But the photos show the Delta fan's connector with those two colours reversed in the connector. IF Delta actually used the "standard" colour codes for the wires from the fan motor, the photos shows they interchanged which connector holes they are wired to, and thus the motor is getting those lines wrong.

You say when you set the mobo header to use PWM Mode it runs full speed all the time, and feeds no speed signal back to the mobo. Then you say if you change...

Paperdoc

Polypheme
Ambassador
Tell us the model number of that fan. Examine the wires from its motor to the connector on the end. A common 4-pin fan for computer case ventilation has 4 wires ending in a 4-hole connector. On one side are two ridges approximately just outside the first and third holes, and these fit around the plastic tongue sticking up from the mobo fan header beside its pins. On the connector, the hole to fit onto pin #4 is beyond the ridges. Wire functions and typical colours are:
Pin 1 - Black - Ground
Pin 2 - Yellow - +12 VDC Supply
Pin 3 - Green - motor speed pulse signal traveling back to the mobo header
Pin 4 - Blue -PWM signal

What you describe MIGHT happen if there is no motor speed pulse signal being delivered via header Pin #3 to the mobo for monitoring. Some mobos monitor that signal on each fan header to detect fan failure, and take certain actions to prevent overheating of critical components.

There's another thing to check. I looked at your mobo manual and it does not seem to have a header with the exact label you cite, nor any indication that is can supply 2A. But SOME headers designed for ues with a water pump do NOT actually do any fan speed control because many water pumps are supposed to run at full speed all the time. So, IF that fan uses no more than 1.0 A max, have you tried it in another fan header?
 

t-nought

Commendable
Feb 8, 2017
3
0
1,510
Hi, thanks for the reply.

You're right that the mb manual doesn't specify, but the specs on the Asrock website say 2A.
https://asrock.com/MB/AMD/X470%20Master%20SLIac/index.asp#Specification
There is an option in the bios to select water pump or fan for the header, but just to see I did try one of the other 4-pin headers with the same result.

Here is the exact fan model: Delta FFB1212EH-PWM 120mm

The wiring does not match what you list above.
Pin 1 - Black
Pin 2 - Red
Pin 3 - Yellow
Pin 4 - Blue

Also, the connector is 4-pins wide instead of 3-pins wide as you describe.
 

Paperdoc

Polypheme
Ambassador
Yes, the photos of the fan show it uses the other common colour coding scheme: Black, Red, Yellow, Blue. BUT there is one oddity there. On a normal 4-pin fan, Yellow is the Speed Pulse signal being fed back on Pin #3, and Blue is the PWM signal supplied on Pin #4 from the mobo. But the photos show the Delta fan's connector with those two colours reversed in the connector. IF Delta actually used the "standard" colour codes for the wires from the fan motor, the photos shows they interchanged which connector holes they are wired to, and thus the motor is getting those lines wrong.

You say when you set the mobo header to use PWM Mode it runs full speed all the time, and feeds no speed signal back to the mobo. Then you say if you change that to DC Mode the fan just does not run. Now, if a 4-pin fan is connected to a header using PWM Mode it gets a full 12 VDC supply from Pin #2 and then depends on receiving the PWM signal on Pin #4 to control its speed. If it fails to receive that signal, it will run full speed all the time. AND, if it fails to send its speed signal back on Pin #3, the mobo will not show a speed and may tell you there is no fan attached (because there is no speed signal). So I'm speculating that, if the two signal lines are interchanged at the connector, the fan gets no PWM signal and sends back no speed, giving you the symptoms you describe.

How to check? What to do? I will assume for now that you do not have access to a simple oscilloscope to examine the speed signal, so I'll suggest another route to experiment. See if you can rig up some temporary wires between your fan's female connector and the pins of the mobo header you are using. In particular, connect the Black line from hole #1 to header Pin #1 (Ground). Connect the Red line from hole #2 to the header Pin #2. Establish a third wire from the Yellow line at hole #4 but don't connect it to anything yet. Now boot the machine into BIOS Setup and go to where that fan header is configured. The fan should run at full speed, but show no speed reading in BIOS. Now, for a short time, touch the wire from the fan's Yellow line to the mobo header Pin #3 and observe the BIOS speed reading. Does it change and indicate a reasonable speed for the fan? If it does, that would confirm that the Yellow wire from the fan is the Speed signal wire and should really be moved to connector position #3. Then by default, we might guess that the fourth (blue) wire really is the PWM line and should be moved to Hole #4.

Shut down and disconnect your temporary wires. IF that temporary test indicates that Yellow belongs on Hole #3, I suggest you interchange the Yellow and Blue wires at the connector. Then re-connect it to the mobo header, turn on, and enter BIOS Setup to observe the info. If that looks "normal", ensure that the header is set to use PWM Mode and try to change the fan speed setting. If you actually CAN change the fan's speed, then surely you must have made the correct connection for the PWM signal line.

I noticed an interesting small point on the Amazon site where this fan is sold. Their photo shows the fan supplied with an additional short cable that uses the other colour code I first listed. Now, that MAY be a simple extension cable in case you need a longer cable to reach the mobo header, but it's not very long. It MIGHT be an adapter cable that does this interchange of Yellow and Blue wire connections, but I cannot tell that from the photo.
 
Solution

t-nought

Commendable
Feb 8, 2017
3
0
1,510
Great, thanks for your help (again). Between work and kids I won't have time to try this procedure until the weekend, but I will try to do some more reading and I will give it a try.