Overclock.net › Forums › Cooling › Water Cooling › CPU Fan Error - No CPU Fan Detected
New Posts  All Forums:Forum Nav:

CPU Fan Error - No CPU Fan Detected

post #1 of 19
Thread Starter 
I recently completed a custom loop with 2 240 rads and 1 exhaust fan using the following parts:
Motherboard: Maximus VIII Gene
Fans (x5): Noctua NF-F12 industrialPPC-2000 PWM
Splitter: ModMyToys 4 Pin Low Profile PCB

When I connect all 5 fans to separate headers, the mobo detects all of them and can read their speeds. When I installed the splitter, I connected the fans to the splitter then the splitter to the CPU_FAN header. Now, on normal startup, it generates an error similar to this one (not mine) and tells me to ignore low fan speed limit in BIOS. I did that and and still throws the error. I had to completely disable CPU fan detection in order to get it to start. The fans still appear to run off the PWM signal but I can't see them on Speedfan or any other hardware monitoring program.

Is it possible to detect speeds and modify fan curves while using a splitter?

Thanks
post #2 of 19
How many pins does the splitter have?
post #3 of 19
Thread Starter 
Quote:
Originally Posted by geox19 View Post

How many pins does the splitter have?

4
post #4 of 19
Check the splitter wiring. Tacho pin on m/b connector needs to only be connected to one (not both) tacho pin on the fan side.

If the splitter actually splits the tacho pin, then tacho counter may get confused by two overlaid tacho signals.

For the 2nd part of your question, yes, tacho readout, as well as PWM and/or DC RPM control work fine over the splitter, as long as it is wired correctly, and with a limitation that you're reading RPM of one fan only.
Edited by cmpxchg8b - 10/4/16 at 10:46am
post #5 of 19
you should be able to see the fan rpm. Most splitters have one lead dedicated to fan rpm do you have that one plugged in? What fan spltter are you using ?
post #6 of 19
Thread Starter 
Quote:
Originally Posted by cmpxchg8b View Post

Check the splitter wiring. Tacho pin on m/b connector needs to only be connected to one (not both) tacho pin on the fan side.

If the splitter actually splits the tacho pin, then tacho counter may get confused by two overlaid tacho signals.

Could you elaborate here? The splitter is connected to the mobo using a 4 pin cable. Won't the splitter need the PWM signal from the mobo AND the RPM signal to be connected?
post #7 of 19
Quote:
Originally Posted by Fleacircus View Post

Could you elaborate here? The splitter is connected to the mobo using a 4 pin cable. Won't the splitter need the PWM signal from the mobo AND the RPM signal to be connected?

Correct, but you need to check splitter wiring. PWM signal has to be split, so m/b PWM pin is connected to PWM pin of every fan. On the other hand, RPM pin must not be split, that is, m/b RPM pin must be connected to one and one only fan. Not all fans.
post #8 of 19
Thread Starter 
Quote:
Originally Posted by cmpxchg8b View Post

Correct, but you need to check splitter wiring. PWM signal has to be split, so m/b PWM pin is connected to PWM pin of every fan. On the other hand, RPM pin must not be split, that is, m/b RPM pin must be connected to one and one only fan. Not all fans.

Then why would the splitter have 6 4-pin inputs and a 4-pin output instead of 5 3-pin inputs, 1 4-pin input, and a 4-pin output? Also, if you're correct, how would I "disable" or rewire 4 of the fans to not send a pin #3 signal?

Thanks for your help.
post #9 of 19
Quote:
Originally Posted by Fleacircus View Post

Then why would the splitter have 6 4-pin inputs and a 4-pin output instead of 5 3-pin inputs, 1 4-pin input, and a 4-pin output? Also, if you're correct, how would I "disable" or rewire 4 of the fans to not send a pin #3 signal?

Thanks for your help.

Don't know. Maybe they want to use one type of fan connector part instead of two. Maybe they know you like modding your toys so they soldered all the wires so you have something to mod.

If the splitter does indeed split the RPM pin (which really is a silly design), you're going to need to cut those extra wires at some point - in the splitter itself, or the cables connecting fans to the splitter. Just clip the pin or the wire.

In fact all splitters I used already came this way, with a missing pin on all fan connectors but one. That's also how you know which fan will report the RPM.
post #10 of 19
Thread Starter 
Makes sense. The splitter was relatively cheap so I may resort to clipping the pins. I'll test the system with 1 fan connected to the splitter when I get home to rule out a faulty splitter.
Thanks again.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Water Cooling
Overclock.net › Forums › Cooling › Water Cooling › CPU Fan Error - No CPU Fan Detected