PC Fans Rev Up on Boot

[roadfox]

Recently my PC has been having my fans go on almost max speed for 1 second when I boot up the pc then acts normally. This has started to happen after I installed my new case fan on the back (No its not the fan itself). I have no idea if this is normal or not and if I should be worried.

Is it normal?
Thanks.

SPECS:
Corsair CX600
3 Case Fans
GT 610 GPU
AMD FX 4130 (With an Aftermarket Antec Cooler)
Gigabyte GA-78LMT-USB3 Motherboard
8GBS of Crusiar Ram
a 1TB Harddrive

 

[junkeymonkey]

you don't blame the fan but it happened after you installed it ?? go in to the bios and check the setting on that fan the new fan may have a sensor that activated and the old one did not

 

[roadfox]

The fan is connected via a molex cable on the PSU, not straight into the motherboard.

 

[junkeymonkey]

did the old fan hook up the same way or to the board? some fans set in a profile will run at full speed intill windows boots and then spin down to there setting but I think there fans that are hooked to the boards fan pins

 

[Paperdoc]

You have two issues here.

First, what you describe is normal. It appears you simply did not notice this behaviour by the fans until you changed the back case fan. For all fans connected to the MOBO, this is the "normal" sequence on boot up: every fan will start at full speed and run that way for a few seconds, then slow down to its routine speed. This is for 2 reasons. First one is that the BIOS is busy and needs to get many things done before it settles down to routine and can take the time to control fan speeds. In the meantime, the fans need something. That something is full voltage (12 volts). Why? Because the fan needs at least 8 or 9 volts just to start up from stopped; after it is running it can slow down and still keep going at reduced voltage.

Second, that fan you have on the back is connected directly to a 4-pin Molex power output from the PSU. That means it will always have the fill 12 VDC supplied to it, and it will ALWAYS run at full speed. There is NO way to change that speed - the PSU has no mechanism for altering the 12 VDC on an output line. Was the old rear fan connected the same way?

 

[roadfox]

did the old fan hook up the same way or to the board? some fans set in a profile will run at full speed intill windows boots and then spin down to there setting but I think there fans that are hooked to the boards fan pins

None of the case fans were connected to the motherboard, all of them are connected straight onto the PSU via Molex. The newer fan uses a 3 pin to molex adapter though.

 

[roadfox]

You have two issues here.

First, what you describe is normal. It appears you simply did not notice this behaviour by the fans until you changed the back case fan. For all fans connected to the MOBO, this is the "normal" sequence on boot up: every fan will start at full speed and run that way for a few seconds, then slow down to its routine speed. This is for 2 reasons. First one is that the BIOS is busy and needs to get many things done before it settles down to routine and can take the time to control fan speeds. In the meantime, the fans need something. That something is full voltage (12 volts). Why? Because the fan needs at least 8 or 9 volts just to start up from stopped; after it is running it can slow down and still keep going at reduced voltage.

Second, that fan you have on the back is connected directly to a 4-pin Molex power output from the PSU. That means it will always have the fill 12 VDC supplied to it, and it will ALWAYS run at full speed. There is NO way to change that speed - the PSU has no mechanism for altering the 12 VDC on an output line. Was the old rear fan connected the same way?

Again all of the case fans are connected via Molex. None are connected to the motherboard.

 

[roadfox]

You have two issues here.

First, what you describe is normal. It appears you simply did not notice this behaviour by the fans until you changed the back case fan. For all fans connected to the MOBO, this is the "normal" sequence on boot up: every fan will start at full speed and run that way for a few seconds, then slow down to its routine speed. This is for 2 reasons. First one is that the BIOS is busy and needs to get many things done before it settles down to routine and can take the time to control fan speeds. In the meantime, the fans need something. That something is full voltage (12 volts). Why? Because the fan needs at least 8 or 9 volts just to start up from stopped; after it is running it can slow down and still keep going at reduced voltage.

Second, that fan you have on the back is connected directly to a 4-pin Molex power output from the PSU. That means it will always have the fill 12 VDC supplied to it, and it will ALWAYS run at full speed. There is NO way to change that speed - the PSU has no mechanism for altering the 12 VDC on an output line. Was the old rear fan connected the same way?

Ok I have decided to see if it is just ONE of the fans, and I have concluded that it is just the CPU fan giving full power then quickly going back to normal. The other case fans give constant speeds.

 

[tech-wreck]

it's fine. is the new case fan quieter in operation than the old one? you probably couldn't hear the CPU fan before.

 

[roadfox]

it's fine. is the new case fan quieter in operation than the old one? you probably couldn't hear the CPU fan before.

Yes it was quieter, the old one sounded like a lawn mower.

 

[Paperdoc]

Ah, you've found the answer. The CPU fan is the only one connected to your mobo, right? So it is the only one whose speed changes. And until you installed a new quiet fan on the back, you could not hear the CPU fan change on start-up.