Different fan plugs - explain please ??

Hiya,

im a bit confused !


some fans plug straight into the 4 pin molex connectors that you get on your psu (12v i suspect)


some have 2 pin plugs that go into your motherboard (how many volts ?)

and aren't some 3 pin ???


The 800mm askas fans i got have a 2 pin connecter on the end of them but then this must be plugged into a 2 pin - molex 4 pin converter ??? Not sure i underatdn that ..... whats the point > Why dont teh fans just have a wire with a female 4 pin molex on them ???

can anyone explain why there are these different types and also what do i need to get if i have a fan that runs on a 12v molex 4 pin but i also want to plug it into the moboard at the same time to get an RPM reading into MBM ?



cheers



Rich

Some fans are 2/3 pins and plug directly into your motherboard. They are still 12 volts, just being powered through the board. The ones with only 2 pins do not have RPM monitoring, only the 3 pins have that, but they are the same thing (2 has 1 wire left out).

Usually you should avoid big fans that plug directly into the boards. The motherboard has trouble providing bigger fans with the watts they need to run. It can also lead to instability when OCing because of the draw.

As far as plugging a 4 pin molex fan into the board, you can, but it wont monitor the RPMs as you believe. The fan has to support RPM monitoring and unless the 4 pin fan has a separate wire to plug into the board for that purpose, you wont be able to do so. There is a mod (forgot where) that you can add monitoring to a fan, but its definately a waste of time.

Your best bet is to run all your fans off the PSU directly. If you have a fan that plugs into the board, and you are really concerned about monitoring RPMs, you can do that.

Also changing a 3pin fan to a 4pin one is rather simple, and you dont need any adapters. If you have any electrical skills at all you can do it.

some fans plug straight into the 4 pin molex connectors that you get on your psu (12v i suspect)

Click to expand...

The headers on motherboards (3 pin standoff connectors) are limited as to how many watts they can drive. Higher wattage fans need to be connected directly to a PC's Power Supply 4 pin molex connectors.

some have 2 pin plugs that go into your motherboard (how many volts ?)

Click to expand...

2 pin plugs are probably NOT designed to plug into your motherboard, since your motherboard has 3 pin connectors. I believe powersupply units are made with 2 pin connectors. I've seen 2 pin connectors used in other applications as well.

and aren't some 3 pin ???

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These 3 pin connectors ARE designed with 3 pin motherboard fan headers in mind. 2 of the pins are for applying power to the fan. if a 3rd wire is attached to the connector and the fan, it is used for sensing and reporting the Fan's RPM.

Not all fans equipped with 3 pin connectors use the 3rd sensing wire, but they still work fine using the 3 pin motherboard header.

Also, SOME fans that use 3 pin connectors exceed the wattage ratings of the fan headers found on motherboards. It is important to make sure you don't power these fans using your motherboard, even if they have the 3 pin connector. if you're using a high wattage fan with a 3 pin connector, get a 3 pin to 4 pin molex adapter so you can safely power these fans directly from your powersupply instead.

The 800mm askas fans i got have a 2 pin connecter on the end of them but then this must be plugged into a 2 pin - molex 4 pin converter ??? Not sure i underatdn that ..... whats the point > Why dont teh fans just have a wire with a female 4 pin molex on them ???

Click to expand...

apparantly, these fans were not wired SPECIFICALLY for your application. If you have any old fans, just cut the connectors off of them as well as off of the fans you wish to use, and splice the 4 pin molex onto the wires of your askas. If your askas use red and black wires, just match them up to the red and black wires on the molex. Also, be sure your askas are 12 VDC fans.

what do i need to get if i have a fan that runs on a 12v molex 4 pin but i also want to plug it into the moboard at the same time to get an RPM reading into MBM ?

Click to expand...

Some 4 pin molex connected fans also have a separate sensing wire connected to a 3 pin motherboard connector so the sensing pin on the motherboard gets the RPM readings. If your fan is not equipped with an RPM sensing wire to begin with, there's nothing I'm aware of that you can do to monitor it's RPMs using the motherboard's headers.

hth

~BdK

bilydkid1970 said:

apparantly, these fans were not wired SPECIFICALLY for your application. If you have any old fans, just cut the connectors off of them as well as off of the fans you wish to use, and splice the 4 pin molex onto the wires of your askas. If your askas use red and black wires, just match them up to the red and black wires on the molex. Also, be sure your askas are 12 VDC fans.

Click to expand...

Like bilydkid made it sound, its really is that easy

One thing to note for 12v fans... Most 3 pin RPM detecting fans use black red and yellow wires. HOWEVER, the red is 12v+ and the yellow is the signal. So if you hook the red wire from your 3pin fan to the red wire to on the PSU, it wont be 12v anymore, itll be 5. You'll want to hook the red on the 3pin to the yellow on the molex, the black to black (either black will do), and the yellow discard. Or if you wanna do the 7v mod, hook the red on the 3pin to the yellow on the molex, and the black on the 3pin to the red on the molex. Again the yellow discard.

If the fan is a 5v 3pin fan, red goes to red, black to black, yellow discard.

oops!!!

let me be clear on the red black thing

i've reused 4 pin molex plugs originally connected to 12vdc fans, wired appropriately.

THOSE plugs had black and red wires, with the other 2 pins in the 4 pin molex being unused.

Reusing plugs like those with simple red and black wires connected to the 12vdc pins on the connector will work as i described.

On a four pin PS molex connector, there are 2 black ground wires, and despite frequent contentions to the contrary, after checking for continuity with an ohmeter, these wires are wired in common (connected) internal to my enermax powersupply. in my situation, swapping the black wires around with each other is no cause for concern.

there is a red wire. 5vdc.

there is a yellow wire 12vdc.

As a side note, there are several ways you can wire your fans if you're wiring your own plugs

If you want to wire it stock - black is ground, yellow is 12vdc.
If you want to wire it at 7vdc for less noise:
connect your fan's ground to the red wire, and positive to the yellow wire.
If your fan will start turning at 5vdc for even less noise:
connect your fan's ground to black and positive to red

hth
~BdK

All the questions have been answered, but a comment:

bilydkid1970 said:

On a four pin PS molex connector, there are 2 black ground wires, and despite frequent contentions to the contrary, after checking for continuity with an ohmeter, these wires are wired in common (connected) internal to my enermax powersupply. in my situation, swapping the black wires around with each other is no cause for concern.

Click to expand...

One of my recent mods included removing all unused wires from a psu so it would fit a mini-rig.
Inside the psu ALL of the ground wires were soldered together in one huge mass of solder

Ground is ground.

I have a questoin:
If I have a temp sensor on my fan, if I plug it into a PSU will the fan change with the temp, or do I have to put it into the motherboard for temp sensor.

There are 3 to 4 pin adaptors with an additional temp sensor plug to connect to the mobo for MONITORING purposes. as far as having your mobo change the speed of the fan with temperatures, that feature only functions if your fan is plugged into the motherboard header and not the powersupply molex connector.

BdK