I am going to upgrading the cooling in my computer, so I bought 3 case fans (the amount my case has room for). They have 4 pin connectors, so I was just going to plug 2 of them into the 2 available fan headers, and then plug the last one into a molex connector considering that they all come with molex adaptors. However, according to this site, your not supposed to because its too much strain on the motherboard? I am not (never have never will) overclocking so is that just for overclockers? My motherboard manual says it will work with 12 volt fans which are what these are.

Haven't had any problems personally, and I have every slot and plug filled. But I suppose it's possible to have a problem.

There isn't so much size difference between cpu and case fans anymore. Mainboard fan connectors are just fine for that purpose.
You should not plug in the type of 12v fan that you have in front of your car watercooler, however
At home and at work ... never a problem with these fans and mobo connectors, just bearings may go bad over time.

Hi there

Basically the same advice as previously posted.
You need ensure that you do not exceed the maximum voltage or current ratings for the fan headers on the motherboard.
One additional factor is whether the external case fan that you are going to connect will produce sufficient back emf (electromagnetic force) when turned from the running (rotating) state to the off state (power off) and whether the motherboard interface will be damaged.
As a rule of thumb I always wire case fans to the PSU using molex connectors, rather than the motherboard case fan headers (it also has the added benefit that if you change the motherboard at some time in the future the case fan wiring is not generally affected).
It is also important not to be over zealous without caution, putting larger non-standard case fans in place can cause problems with significant back emf, inrush current on start up, etc.

Best of luck

Chris

I always plug them in with the molex adapters to the PSU, not because plugging them into the mobo would not work, but because the mobo doesn't control them properly, they're always running at low speed, and they have no effect on cooling.

From an electrical standpoint it is always safer to use the molex adapters, but if they're regular fans and the mobo can provide the voltage they need, there should not be any problem.

Hi,

I use a Power controller for the system fans. Most have the interface(s) connections for MB interconnection for speed indications. The use of a Power Controller will facilitate the fans so efficient flow of the cooling for your chasis. I do suggest that when quality fans are used along with the controller the noise will be limited .

If you do use one for the CPU then make certain it does have limit controls for lower & upper. Some are just potentiometers that will go to zero, which would be a no-no. Look for PWM type controllers, more money but worth the investment.