Confused about 3 pin and 4 pin molex connector

[princelemon]

I'm buying a few fans for my case. Jab-tech ask me to choose between a 3 pin header and a 4 pin molex. What is the difference?

A local computer store only sells 3 pins.

I don't know what the difference is. I don't know what are each type used for. I don't know what advantage/disadvantages are.

Can anyone help explain it for me?

 

[DaveSimmons]

4 pin connects to your PSU, it's the same socket as a CD/DVD drive, 3 pin connects to the motherboard.

3 pin is a bad idea for 92cm - 120cm fans or attaching a lot of 80cm fans at once because they draw too much power and can damage the motherboard.

A "fan controller" that goes into a drive bay might have either kind of connector, if you are using one look and see what it needs.

 

[princelemon]

I see. Thanks.

So it's better and safer to just go for the 4 pin?

I will have 4 case fans. Is there enough connectors on the PSU to connect all four case fans?

Also, I'm going to get a 120mm fan for a Thermalright si-120 heatsink. Is it still better to get a 4 pin for that?

 

[Harvey]

Originally posted by: DaveSimmons
3 pin is a bad idea for 92cm - 120cm fans or attaching a lot of 80cm fans at once because they draw too much power and can damage the motherboard.

Sorry, but that's bad info. Molex specs the contact rating for typical 25 mil square pins on 0.1" centers is 2.5 amps. A typical typical larger fan draws maybe 140 - 160 mA.

There's no way you'll damage your motherboard or anything else with this connector in that application.

The three pin connectors are often used with fans having a speed sensor or control. If the fan you're using doesn't require that, you can use whichever connector came with the fan, as long as your motherboard has the mating connector for it.

 

[DaveSimmons]

A low speed 120cm might only need 150, but I just checked a Panflo I have and it's labeled 650 (0.65A).

People have posted here about burning out motherboard connectors after attaching 92 - 120cm fans, so regardless of how the pins are specc'd it isn't always going to work.

Perhaps it's more accurate to say a motherboard fan connector should be safe to use with all 80cm fans and many (but not all) larger fans.

 

[princelemon]

So . . . in conclusion . . . ? ?

It's safe to use either connectors? Only if I want to buy a fan controller, I would need to consider either one or the other?

 

[DaveSimmons]

FIrst, check how many fan connectors your motherboard has besides the one for the heatsink-fan. If iy only has 1-2 extra connectors then you can only get 1-2 fans that use a 3-pin connector (any others must be 4-pin and attached to the power supply)

Next, if you are buying any 92cm or 120cm fans, either find out the power draw ahead of time to make sure it is safe for a motherboard (up to "0.15A" should be safe) -or- just get 4-pin connectors and connect them to the power supply.

Short answer: 4-pin is always safe, 3-pin is safe if the power draw is 0.15A or less and you have enough connectors on your motherboard.