Please help this newbie with his molex question...

[nstemi]

OK guys, I will say off the bat that I am a doctor-in-training and am learning about hardware as a hobby. I thought it would be fun and educational to build my first PC. So after extensive reading (especially on this forum -- thank you everyone!). I've ordered my supplies, and I'm ready to begin -- except that I hit a very small snag.

My case is the Antec Three Hundred Illusion and my mobo is the ASUS P8P67. The Antec case has 4 x 120 mm cooling fans. Each fan comes with two wire connectors. One is the power connector -- a 4-pin molex, and the other is a tiny wire with a little switch/slider which slides between H and L (Hi and Lo) for fan speed, I presume.

The problem for me is the molex connector. The molex connector on the case fan, fits beautifully into the 4 pin molexes on my Antec 520c PSU.

However, unlike the 4 pin molexes that come out of my PSU (which are single connectors), each plastic molex connector that feeds each of my case fan has 2 ends. One one end, it has 4 pins (see below)

....and on the other e it has 4 holes (almost as if I could piggyback another molex into that). I've attached a picture for both ends of the molex connector for you to see.

My question is this: Can I connect the 4 pin molex directly from my PSU to one of these two-sided molex connectors on my case fan, and then directly connect the other connector from another case fan to the same molex, so that I can power multiple case fans directly from a single molex from my PSU, instead of going through my motherboard?

The reason I ask this question is that my motherboard has only 2 case fan connectors named (CHA_FAN1 and CHA_FAN2). These 4 pin connectors are much smaller and will not fit the standard 4-pin molex that feeds my case fans. So without the use of some fancy adaptor, I will not be able to hook up my case fans to my motherboard, and even so, I will not be able to hook up more than 2 of my case fans. Below is a pic of my motherboard connector, as you can see will certainly not connect to the molex that feeds my case fans.

I really hope you guys understood this question, and I apologize for this newbie question, but any help will be most appreciated.

 

[mnewsham]

Yep just daisy chain em

 

[BoomerD]

Yep just daisy chain em

zakly...

 

[oynaz]

Remember to put some thought into which way you turn the fans. You want to blow air over the motherboard and videocard, so you would normally have some fans sucking air into the case, and some blowing it out.

 

[mfenn]

Yeah, you can daisy chain them just fine. You would have to have a lot of fans to overload a Molex connector.

The small 4-pin connectors on your motherboard allow you to control the fan speed via the BIOS or Windows software. If you want to use them, you can either buy fans with 3-pin/4-pin connectors or buy Molex to 3-pin adapters. That's totally optional though.

 

[Paperdoc]

Yes, daisy-chain all four case fans from one PSU output. Then use each fan's 3-position switch to set it to a fixed speed. You can re-adjust those settings as you see fit, depending on the case temperatures you get. Antec often provides this type of case fan.

Connecting the fans to the mobo's CHA_FAN1 output probably won't work well. Here are a couple of the issues if you try. One, as you anticipate, is that the fan connectors don't match up and an adapter is needed. Those exist. However, the mobo pinout has 4 pins, and that means it was designed for a "4-pin fan". That type of fan is supplied from the mobo pins with connections for Ground, a constant +12 VDC, a PWM speed control signal, and a return speed signal generated in the fan and sent back to the mobo. A small circuit inside the fan case uses the PWM control signal to vary how much current (based on time) actually flows from the +12 VDC supply through the motor to Ground, thus accomplishing speed control. However, that is NOT how your Antec fans work. They are similar to a "3-pin fan" that depends on having a supply to them of varying DC voltage on the two wires that feed them. That is how their speeds are controlled. They do NOT have any internal circuit to use the PWM signal. The particular fans you have are slightly different in this sense. They are designed to receive a full 12VDC on their two leads at all times. Then the little switch-on-a-cord and a couple of resistors actually reduce the voltage to the fan motor for speed control, similar to the way a 3-pin fan's speed is controlled. BUT this one is not intended to work with a mobo controller - it is designed to get its power from the PSU's Molex outputs directly.

While it is true that, with the proper adapter, you could feed the necessary +12 VDC and Ground leads from the mobo's 4-pin output, that still would not give you any speed control by the mobo - speed control still would be done with the little 3-position switches. So there is NO advantage to feeding from the mobo, and there is a disadvantage. The mobo pinout has limited capacity - probably no more than 2 fans wired up to it - whereas the Molex PSU output has LOTS of capacity for several fans, daisy-chained as discussed.

 

[mfenn]

Connecting the fans to the mobo's CHA_FAN1 output probably won't work well. Here are a couple of the issues if you try. One, as you anticipate, is that the fan connectors don't match up and an adapter is needed. Those exist. However, the mobo pinout has 4 pins, and that means it was designed for a "4-pin fan". That type of fan is supplied from the mobo pins with connections for Ground, a constant +12 VDC, a PWM speed control signal, and a return speed signal generated in the fan and sent back to the mobo. A small circuit inside the fan case uses the PWM control signal to vary how much current (based on time) actually flows from the +12 VDC supply through the motor to Ground, thus accomplishing speed control. However, that is NOT how your Antec fans work. They are similar to a "3-pin fan" that depends on having a supply to them of varying DC voltage on the two wires that feed them. That is how their speeds are controlled. They do NOT have any internal circuit to use the PWM signal. The particular fans you have are slightly different in this sense. They are designed to receive a full 12VDC on their two leads at all times. Then the little switch-on-a-cord and a couple of resistors actually reduce the voltage to the fan motor for speed control, similar to the way a 3-pin fan's speed is controlled. BUT this one is not intended to work with a mobo controller - it is designed to get its power from the PSU's Molex outputs directly.

Most every motherboard I've seen allows you to fall back to voltage control via a BIOS setting. Works fine IMHO.