Strange boot-up sequence

[Nightsilencer]

Hey guys.

I have a problem at start-up that started happening just a few minutes ago when I added an extra fan to the side plate of my case.

here's what happens: I press the power button, computer turns on and then after 2 or 3 seconds it shuts itself down, and after another second or 2 it turns itself back on again and boots up normally.

This DID NOT happen before buying the fan and DOES NOT happen if I unplug the fan. I've tried it.

I don't know if there's anything wrong with this issue... it just seems strange... could it be PSU issue? Well, it would be strange... I don't believe this fan could cripple my PSU... it must not be that power hungry, it's just one of those fans that plugs into those 3-pin thingys directly on the mobo.

For reference, here are my specs:

Intel E8400 @ stock

GF 8600GT (does not require aditional power, just what comes from the PCI-E bus)

Asus P5Q Pro

2x2GB Transcend RAM 800mhz

Deer (generic?) 480w PSU.... it came with my case.

Extra: Just one cheap exhaust fan at the back of my case and this new fan on the side of my case.

As you can see, I don't think my system is that power-hungry... especially since I don't overclock (yet).

I'm a bit worried though, as this started happening as soons as I added this new fan I bought today... I fear my PC could be under perfoming because of this strange ocurrence.

But could a simple low-power fan cause this?

Thoughts?

 

[Paperdoc]

It may not be fan power, but attempted speed sensing and control.

The third wire from fan to mobo is a fan speed signal. A lot of mobo's in their BIOS monitor the speed of several fans and try to control them based on temperature sensors in the system. I uses a sensor built into the CPU, for example, to control the CPU's cooling fan speed, and checks that this fan is working by reading its speed signal. It can do similar things for the PSU fan (if the PSU has a wire set for this) and for up to 2 case fans.

First of all, check where on the mobo you plugged in the new fan. It definitely should be on a connector marked "CHA_FAN1" or something similar. It should NOT be on CPU_FAN or PWR_FAN. Plug it into the wrong mobo connector and the BIOS gets confused because it will run the fan but think it is monitoring and controlling the speed of a different fan!

Next, go into the BIOS and look for where it controls the various fans. Whichever you have it connected to, (say, CHA_FAN1, or Case Fan#1), look closely at its control options. You may have things like "Auto" (the BIOS does things its pre-programmed way), "Custom" (you can set your own temperatures for starting, stopping and min and max fan speeds), "Full Speed" or something like that (the fan always runs a full speed and the BIOS does not try to control it, but it may continue to check that it is running) or "Ignore" (the BIOS ignores this fan's speed readings). You can try telling it either to ignore the fan (the CHECK that it still runs!) or to run at full speed always. See if that makes any difference to the start-up sequence.

 

[HeXploiT]

Bad bad bad. Do not try that fan again or you risk burning something out.
Now let me say that it is entirely possible that adding that last fan is pushing your psu over the edge.
I however would assume first it's the fan and try another fan first. If it does the same thing with another fan then you'll know you just need more power. With that setup I would recommend ATLEAST a 500w quality power supply.
Again it probably is that your power supply is too weak but always assume the worst first.

 

[Nightsilencer]

Paperdoc, I checked it, the fan is connected to CHA_FAN 2...but could this be the problem? should it be on FAN nr 1?

 

[Paperdoc]

Originally posted by: Nightsilencer
Paperdoc, I checked it, the fan is connected to CHA_FAN 2...but could this be the problem? should it be on FAN nr 1?

This is probably OK. Should not matter whether it's #1 or #2. But just to experiment if you want (and if the wires reach) you could plug into CHA_FAN1 and try.

Perry404 says you may really have a bad fan, or a PSU with too little output, so consider that, too.