3 pin Fan Why

[thescreensavers]

If I plug a 3 pin fan to the connector on the mobo it spins at full speed but if i connect it to an an adapter and to the molex connector it spins much slower even connected to the main molex from the PSU why?

 

[thebigdude]

Mobo? Fan? PSU?

 

[JeffreyLebowski]

What voltage is the fan rated at? It's possible that the molex adapter is for 5 volt items. and the fan requires more juice????

 

[Sniper82]

Originally posted by: JeffreyLebowski
What voltage is the fan rated at? It's possible that the molex adapter is for 5 volt items. and the fan requires more juice????

Sounds about right for me. The 3rd wire(RPM) is useless when hooked to the PSU. It's main use AFAIK is to let the mobo know what RPM it's running at, and if that RPM ever reaches slower(or zero) it triggers the mobo that it failed and it sends a alarm or shuts the system down. If it has that feature and its enabled.

 

[thescreensavers]

i connected it to the 12volt molex, my psu ,mobo and spec of my computer in my sig, i dont know about the voltage of the fan uses but i thing its 12 almost positive it is

 

[PurdueRy]

Originally posted by: thescreensavers
i connected it to the 12volt molex, my psu ,mobo and spec of my computer in my sig, i dont know about the voltage of the fan uses but i thing its 12 almost positive it is

Could be wrong here but I think the 4 pin lines that go to fans and hard drives and such are 5V

 

[unfalliblekrutch]

Originally posted by: PurdueRy

Originally posted by: thescreensavers
i connected it to the 12volt molex, my psu ,mobo and spec of my computer in my sig, i dont know about the voltage of the fan uses but i thing its 12 almost positive it is

Could be wrong here but I think the 4 pin lines that go to fans and hard drives and such are 5V

Yea, I'm pretty sure fans are 3.3v or 5v.

 

[Sniper82]

the 4 pin molex that connects to Hard drives and fans have a 5v and 12v line on them. Most 4 pin to 3 pin adapters feed off the 12v line but there are some you can buy that feed off the 5v line. I also think most 80mm fans and bigger are 12v. Guessing here but I also think they just have resistors in them to control certain RPM's that the manufacture of the fans want.

The yellow is the 12v and the red is the 5v. On the adapter you have is the red wire(or whatever color) from the 3 pin connector going into the red or yellow wire on the 4 pin molex?

 

[thescreensavers]

I am using the yellow one and checked with a multimeter and it was 12 volts. I made an 3pin adapter with two connetors to the fan and one to the mobo. I made 2 of them noe i there any why slow them down thru the 3 pin connector.

i got speed fan but it only helps the rear fans and no other fans but it shows up as 3 fans but i cant lower the other 2

 

[thescreensavers]

it says that the rated voltage is 12v and starting is 6v. but when pluged into a 12 volt molex it spins slower then thru the 3 pin.

 

[thescreensavers]

bump

 

[shabby]

Whats the voltage on the 3pin mobo connector? If both the mobo and molex connector show 12volts i dont see how it can spin fast on one and slow on the other.
I just rewired one of my fans with a molex connector to my 3pin fan controller and all went fine, dont see why you're having a problem doing the opposite.

 

[Zepper]

The red wire on the fan must be connected to the yellow wire (+12V) coming from the PSU. The yellow wire from the fan is not connected (speed sensor wire). The black wire from the fan is connected to a black wire from the PSU. Some molex to three pin adapters are wired for seven volts (black wire of fan to red wire from PSU - red wire from fan to yellow wire from PSU) or 5 volts (red wire of fan to red wire from PSU, black to black). You really need to trace connections or measure with DMM to be sure you're getting the full 12V.

Most PC fans are 12V, but you can find 5V ones out there which are mostly used in cheap HSF combos or tiny fans used in laptops and the like.

.bh.

 

[Davegod]

If that PSU molex connector is marked with something like "Fan only", it's the PSU varing the power it gives down that cable based on the temperature of the PSU (and hence how hot it's guessing your case temp is).

 

[thescreensavers]

no, I don?t know why but it just does not spin fast on the Molex then the 3 pin. I have the thermaltake Xaser case and I modded the fans to work with the fan controller which was Molex only. But the Molex cable plugged into a 3 pin. On the fan controller there are 4 channels 2 and 3 are for 2 fans or more 1 and 4 are for one. So I hooked it up the 2 and 3 and now i can control them I am just wondering why it spinned slower on a Molex then the 3 pin of the mobo.