Can a case fan be run without the 4 pin molex plugged into a PSU?

[Germz]

I know, this sounds like a stupid question but it is something that i need to know. To make a long story short, i plugged in AC Ryan 120mm Blackfire fan's 3 pin connector into the mobo's SYS FAN header and unplugged the molex. Before it was running plugged into the 4 pin molex via an adaptor. Plugged in & turned on the PC, all the fans including this one are spining but system wont boot. The monitor would turn on and then turn off, thats it. So i plugged the fan back into the 4 pin molex & into the PSU and system booted fine. So is possible to run a case fan without the 4 pin molex plugged in and by just having fan's 3 pin connector plugged into mobo? If yes, why cant i do it? Can anyone answer this?

 

[LotusMan101]

lol

 

[Zap]

Originally posted by: Germz
So is possible to run a case fan without the 4 pin molex plugged in and by just having fan's 3 pin connector plugged into mobo? If yes, why cant i do it? Can anyone answer this?

Yes it is possible.

As to why it doesn't work on your setup, could be a number of possibilities. You may have plugged it in wrong (maybe backwards, easy to do when working inside your case with components all around), causing a ground loop. This is a sure-fire way to cause things to not work. Alternately, the fan may be trying to draw more power than the motherboard can supply through that header. This used to be a BIG problem back in the Pentium III and Athlon days, though not so much now.

 

[Germz]

Originally posted by: LotusMan101
lol

I dont really see whats so funny about this.

Yes it is possible.

As to why it doesn't work on your setup, could be a number of possibilities. You may have plugged it in wrong (maybe backwards, easy to do when working inside your case with components all around), causing a ground loop. This is a sure-fire way to cause things to not work. Alternately, the fan may be trying to draw more power than the motherboard can supply through that header. This used to be a BIG problem back in the Pentium III and Athlon days, though not so much now.

Everything was plugged in properly, i actually triple checked. The thought about the fan not getting enough power has also crossed my mind. I says that the fan consumes only 0.32W but i assume the mobo should have plenty of power: I have the 24 pin ATX and 8 pin EPS connectors from the PSU plugged into the board. The PSU is a 600W Seasonic M12 that powers an e8400 (@ stock for now), IP35 Pro, HD 3450, 2 HDDs, 2 optical drives and 2 case fans. There should be plenty of power left. May be power is not the issue, then what is?

 

[Zepper]

First question is why anyone would buy AC Ryan fans when so many known quantities are out there that aren't just repackaged Chinese junk? IAC, I suggest you RTFM. I understand the LEDs are powered separately from the fan motor, so it is likely that it has to be connected differently from most other fans for that feature to work. The AC Ryan pages spend a lot more time talking abuout the various UV and LED features than the fan itself - that's a big clue right there.

First off, one should never hook both the psu Molex connector AND the 3-pin mobo connector at the same time unless you are absolutely sure that they are not wired in parallel, use one or the other.

.bh.

 

[Germz]

Originally posted by: Zepper
First question is why anyone would buy AC Ryan fans when so many known quantities are out there that aren't just repackaged Chinese junk? IAC, I suggest you RTFM. I understand the LEDs are powered separately from the fan motor, so it is likely that it has to be connected differently from most other fans for that feature to work. The AC Ryan pages spend a lot more time talking abuout the various UV and LED features than the fan itself - that's a big clue right there.

First off, one should never hook both the psu Molex connector AND the 3-pin mobo connector at the same time unless you are absolutely sure that they are not wired in parallel, use one or the other.

.bh.

yea, i bought these 2 fans a while ago and just reused them for a build i'm doing for someone, i know they are not the best quality but was just trying to save the guy some cash.

If you read my post, i didnt plug in the 3 pin and the 4 pin molex together. It was done separately. I'm trying to run these fans just off the 3 pin connector no molex.

 

[aigomorla]

Originally posted by: Germz

Originally posted by: Zepper
First question is why anyone would buy AC Ryan fans when so many known quantities are out there that aren't just repackaged Chinese junk? IAC, I suggest you RTFM. I understand the LEDs are powered separately from the fan motor, so it is likely that it has to be connected differently from most other fans for that feature to work. The AC Ryan pages spend a lot more time talking abuout the various UV and LED features than the fan itself - that's a big clue right there.

First off, one should never hook both the psu Molex connector AND the 3-pin mobo connector at the same time unless you are absolutely sure that they are not wired in parallel, use one or the other.

.bh.

yea, i bought these 2 fans a while ago and just reused them for a build i'm doing for someone, i know they are not the best quality but was just trying to save the guy some cash.

If you read my post, i didnt plug in the 3 pin and the 4 pin molex together. It was done separately. I'm trying to run these fans just off the 3 pin connector no molex.

You just need to splice the wires on a 3pin header.

Do you have an old fan to splice the header off? If you dont, it maybe just easier picking up a 4 dollar yate @ jab-tech.

 

[Germz]

yep, i have a couple old 80mm crap fans i'm not using. Any idea which wires need splicing?

 

[aigomorla]

Originally posted by: Germz
yep, i have a couple old 80mm crap fans i'm not using. Any idea which wires need splicing?

try to keep the color the same.

Red with red

Black with black.

The Yellow is a tach cable, you can splice that if you want TACH.

But make sure you keep the red with red and black with black, or the fan will spin backwards due to the mix in polarity.

 

[Germz]

cool, thnx

 

[Zepper]

You don't need to splice any wires. The 3-pin LED connector stacks onto the 3-pin power connector. If you do stack them together, then both get the same power. For the LEDs to retain full brigtness while allowing the fan speed to be controlled, you unstack the connectors and plug the LED connector onto uncontrolled power and the power connector to the controlled voltage. You can use one of the 3-pin to Molex (PSU) adapters on the LEDs to do that. But NONE of this should cause your system to die unless you have some polarity reversed or some short somewhere. Some systems won't work without a properly working fan with a working speed sensor connected to the CPU fan header, so if you were trying to power the LED lead separately and from the CPU fan header, then that might be your problem. You can usually disable that CPU protection feature in the BIOS setup.
. Decent fans are polarity protected with a diode, so they won't run if plugged in in a reverse polarity - usually you'd have to force the connector to do that as they have guides to line them up properly.
. If you could post a pic (closeup of all the fan connectors you've been using) we could possibly tell what's going on. Maybe one of the index guides has been broken off allowing a reverse condition. Or maybe the stacking thing can allow a reversal. Accidental shorts can definitely cause the full system not to run.

.bh.

 

[Germz]

thnx Zepper. This has nothing to do with a CPU fan though, i have a Zalman 9500 plugged in into the CPU FAN header and its working fine. This is problem only affects the SYS FAN header when i plug in the fan's 3 pin in there without the molex.

I took some pics of the fan but i dont know how to uplad em in this forum, anyone know how?

 

[Zepper]

Just post them to a site like photobucket.com and post the links to them in a message here.

.bh.

 

[Germz]

ok, got the photos uploaded

this is how the fan looks like with everything disconnected:

http://i462.photobucket.com/al...germz0004/DSCN6617.jpg

note that it has 1 3 pin female and 1 3 pin male on one set o wires and 1 3 pin on another and 3 pin male to 4 pn molex adaptor

this is how i had it running with no problems with the 4 pin molex adaptor plugged into PSU

http://i462.photobucket.com/al...germz0004/DSCN6618.jpg

and finally this is how i had it when i had it plugged into SYS FAN header on mobo

http://i462.photobucket.com/al...germz0004/DSCN6619.jpg

 

[Zepper]

Thanks, from your pix, it looks like it should work just fine connected with or without the adapter and the LED polarity keying looks to be intact. I'm DLing your mobo manual so I can scope out the Fan headers. When you connected to the mobo fan header, did you try it both with and without the LED connector stacked? If so, did it work differently one way or the other?

.bh.

 

[Zepper]

And have you tried a known-good fan on the SYS_FAN header to eliminate the mobo as the problem. It looks like that mobo has only one header for a system fan, the other header is reserved for a PSU fan connector (possibly a Gigabyte branded one so I'm not sure what the function of it is - perhaps only has speed sensor pin working along with ground so only suitable for warning of PSU fan failure). Any way, the one header for a case fan is the one toward the SATA port connectors and marked SYS_FAN. If you connected the main 3-pin connector from the Ryan fan to the PWR-FAN header right next to it (or just the LED connector), the mobo may not boot because it would seem that the PSU fan was dead as that connection may not provide any power (PSU fan gets that internally to the PSU) only the speed detection...

.bh.

 

[Germz]

There is a bit of misunderstanding regarding the mobo, this not for my Gigabyte board. As i mentioned above, this is for Abit IP35 Pro in a system i'm working on for someone. That board has 1 CPU FAN, 1 SYS FAN and 4 AUX FAN.

I haven't tried it withoout the LED set of wires (the other 3 pin connector) not have i tried another working fan (which i shoul've done first) to eliminate the possibility of bad header on the mobo. I will try both of these and post back here.