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PWM fan mod problem

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System5

New Member
Joined
Nov 1, 2012
Hello
i bought a 1.74 amp delta fan and my motherboard supports 1 amp only, so i removed the red and black wires and connected it to the molex and the yellow and blue wires to the motherboard's system fan header, the fan works and i can see the fan's speed but can't control it's speed, neither through bios or fan control software, i thought the fan is bad, so i tried another pwm fan that is less than 1 amp using the same method and it did the same thing, so i connected that fan directly to the motherboard and pwm worked fine, if i disconnect the red and black wires from the fan header pwm doesn't work, anyone knows why this is happening?my mb is H81M-S2PV rev. 1.0
 

don256us

Uber Folding Senior
Joined
Jul 17, 2003
So PWM modulates how often a pulse of power is sent to your fan. E.G.
Slow = |____|____|____|____|____|
faster = |___|___|___|___|___|___|
Faster yet = |__|__|__|__|__|__|__|
Fastest = |_|_|_|_|_|_|_|_|_|_|_|_|
Plaid = ||||||||||||||||||||||||||||| Note: always slow down first when coming out of plaid.

Each pipe "|" would be a pulse of electric with each underscore "_" being a pause.

This is how the speed is regulated. You connected the monitor but removed the ability to control. I think that the black wire would be sent a faster or slower pulse of DC power based on settings and the sensor. You aren't using that black wire so no change is made.

Note: Why in the heck would you want a delta fan on your system? Aren't they like loud as all get out? I would go with a large 120/140mm fan spinning slower and more silent. But that's me and my usage needs.
 

dejo

Senior Moment Senior Member
Joined
Nov 11, 2001
The new Phanteks t30-120 is close and controllable without the current needs of a Delta. It is not a Delta though
 

GotNoRice

Member
Joined
Dec 6, 2002
You should look at getting a PWM hub with external power input. Example:

https://www.silverstonetek.com/product.php?area=en&pid=526

I use one of these to power 8 PWM fans using a single PWM header. (my 360mm radiator uses 6 fans just on it's own). It gets power from a SATA connector, but replicates the power output to each fan connector based on what it gets from the PWM input. I don't run any individual fans that consume that much current, but all my fans combined almost certainly consume more than that. (most are in the 0.30a - 0.60a range). The hub claims to be able to support up to 4.5A total, even on a single port, so it should be able to do 1.74a.

I'd still be somewhat wary though. About 10 years ago I ran a 120mm Delta fan in my computer using a manual fan controller (external knobs). The fan was model FFB1212EH, also 1.74A, and probably similar to the one you are trying to use, but only 3-pin. It ended up burning up that channel on my manual fan controller and that's when I stopped using it.
 
OP
S

System5

New Member
Joined
Nov 1, 2012
So PWM modulates how often a pulse of power is sent to your fan. E.G.
Slow = |____|____|____|____|____|
faster = |___|___|___|___|___|___|
Faster yet = |__|__|__|__|__|__|__|
Fastest = |_|_|_|_|_|_|_|_|_|_|_|_|
Plaid = ||||||||||||||||||||||||||||| Note: always slow down first when coming out of plaid.

Each pipe "|" would be a pulse of electric with each underscore "_" being a pause.

This is how the speed is regulated. You connected the monitor but removed the ability to control. I think that the black wire would be sent a faster or slower pulse of DC power based on settings and the sensor. You aren't using that black wire so no change is made.

Note: Why in the heck would you want a delta fan on your system? Aren't they like loud as all get out? I would go with a large 120/140mm fan spinning slower and more silent. But that's me and my usage needs.

what if i connect the black, yellow and blue wires to the system fan header and the red wire to the molex, will the fan work without any damage to the motherbord?

Edit1: i tried it and it didn't work, fan is at full speed and no control

Edit2: thanks everyone, i found out the cause of this issue, it's the motherboard's system header, pin 2 is responsible for +12v and speed control, i can't use that pin because of the fan's high amperage, that's why i can't control the fan, but on the cpu header pin 4 is speed control, i didn't expect that the headers are different,