Can you use a 4 pin CPU fan on a motherboard with a 3 pin connector?

[buckdog05]

I just replaced the heatsink/fan on my computer because I had replaced the original CPU with a dual-core (Athalon X2) and the old fan was running very loudly. I searched Newegg for a new heatsink/fan and ended up getting the ARCTIC COOLING Freezer 64 Pro 92mm CPU Cooler. Here is the Newegg page for the heatsink/fan:

http://www.newegg.com/Product/Product.aspx...N82E16835185125

It worked perfectly for most of the day, but when I went to watch a movie this evening, the computer had turned itself off. When I turned it back on, it came up with a message on the screen that said, "the CPU fan has failed and your computer will turn off in a few seconds to avoid damage to the CPU."

Before the computer turned off, I took the case off of the side of the computer, and the fan was running (albeit slowly).

When I installed the fan, it had a 4 pin plug, and the motherboard (an Asus inside of a Compaq computer), only has a 3 pin connector. There were guides on the connector that fit with the pins on the motherboard, but I had to leave the forth pin hold just hanging off of the side.

I did some research and it turns out that the 4th pin is used to control fan speed. The old fan, however, did not always run at the same speed and only had 3 pins.

Do I need to buy some kind of converter to use my new heatsink, or was what I experienced just a fluke? The computer is running right now, so I figure that it will be good for a least another 8 hours. Is it safe to leave it on?

I was also thinking of keeping the new heatsink but putting the old fan on it. Do you think this would work?

Thanks, and happy holidays!

[Groonx]

The 4th pin is probably a PWM pin that allows you to adjust the fan speed from Windows. Otherwise you can do it in the BIOS or sometimes physically inside the case.

[Pulse-width modulation (PWM) allows for information or control according to the way the dog is barking.]

In the BIOS (and maybe also via software that acts between you and the BIOS), you can set your fans to S.M.A.R.T. or not. SMART sounds good, but sometimes SMART ain't so smart. It all depends on your settings.

You could enable SMART and enable an alarm or system shut-down, and if you messed things up you could create a situation like this:

— The fan is SMART, and only turns as required. When the system is cool, the fan might not turn at all.

— The system is SMART, and recognizes a fan that fails to operate.

— There is a fan not turning (our first item here) and so either a siren sounds or the whole system shuts down.

The remedy might be to go into the BIOS and in HEALTH see what you can see about CPU temperature and about SYSTEM temperature. If they are around 30º, that is very cool. If they are around 80, you have a serious temperature problem. But I would look right in the BIOS, because software might report the sensors incorrectly. I would trust what I see in the BIOS.

Okay, once you feel confident that your temperatures are just fine, then you can adjust your fan controls (in the BIOS) accordingly. If you turn OFF the SMART control to either of your System or CPU fans, you will cause that fan to turn at full speed, all the time. That might be a perfectly good way of doing things, actually.

— Is it too loud for you? Then you might not like it that way.

— Will it reduce the life of the fan? Not necessarily at all [because the fan might be built to spin at full speed as default, which, in that case, would be its most efficient speed].

— Will it use more energy/electricity? Yes, but negligibly. (Fans are among our most efficient electrical gadgets.)

I hope there is something in there that is useful to you.

Edited December 26, 2008 by Groonx

[weEvil]

Yes you can. Make sure you pug it in correctly, maybe you plugged it in backwards. The wire colors have to match.

Since the socket is not the same, it might be loose. Get a glue gun, put it to the lowest temperature (removable later) and put a bead of hot glue to hold the fan connector to the plastic base.

[bonestonne]

you can't set a fan with SMART settings, that's just for Hard drives.

you can set the BIOS to give you fan failure warnings though. this way, if the fan ever fails to start up, you system will shut itself down to prevent overheating.

the fan speed control is actually Smart Fan settings, it has nothing to do with S.M.A.R.T.