p4p800 SE hardware problem

  • Thread starter Thread starter Piero
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Piero

I have a P4P800 SE motherboard. Asus probe alarmed me because chassis fan
and power fan speeds are zero. Cpu fan speed is ok. I changed fans, but i
did not solve my problem.

I did a test with a multimeter and i found out that chassis and power fan
voltage gnd/+12v connector is 10volt without load and it's 1 volt with a
12volt, 2watt fan load.
Asus user guide tells the fan connectors support cooling fans of 350mA -
750mA (8.88W max).

Bios hardware monitor is ok and all volatages are good, but chassis and
power fan speeds are [N/A].

I have solved fan problem connecting my two fans (max 4W) to a free 12volt
molex for harddisk power supply connector with an adaptation, but in this
way i have not monitor fan speed anymore.

Can someone explain me what is it happened to fan connectors on my
motherboard?

Thank you
 
"Piero" said:
I have a P4P800 SE motherboard. Asus probe alarmed me because chassis fan
and power fan speeds are zero. Cpu fan speed is ok. I changed fans, but i
did not solve my problem.

I did a test with a multimeter and i found out that chassis and power fan
voltage gnd/+12v connector is 10volt without load and it's 1 volt with a
12volt, 2watt fan load.
Asus user guide tells the fan connectors support cooling fans of 350mA -
750mA (8.88W max).

Bios hardware monitor is ok and all volatages are good, but chassis and
power fan speeds are [N/A].

I have solved fan problem connecting my two fans (max 4W) to a free 12volt
molex for harddisk power supply connector with an adaptation, but in this
way i have not monitor fan speed anymore.

Can someone explain me what is it happened to fan connectors on my
motherboard?

Thank you
Click to expand...

There are three fan headers. The CPU fan header is fed by a
transistor, and the transistor is controlled by Q-fan. The
other two fan headers are "dumb", and as far as I know, they
are fed directly from the single +12V pin on the ATX 20 pin
connector. (I checked this on my P4C800-E, by using
an ohmmeter, and I got zero ohms when measuring from the +12V
pin on the 20 pin power connector, to the +12V pin on the fan
header.)

The first thing to check, is unplug the computer from the
wall, then unplug the ATX 20 pin connector, and examine it
for damage. See if any of the plastic is melted or there are
burn marks. If everything looks OK, you could measure with
your ohmmeter, from the +12V pin on the ATX 20 pin, over
to the fan header, and see if the copper track on the
motherboard is still in one piece or not. For example, if
you shorted a fan header accidently, enough current would
flow from the ATX 20 pin power connector, to burn out the
fan header copper track. I've never seen a picture of a fuse
on the motherboard, for the fan headers.

If your CPU fan header fails, that is a different story,
as then it could be the MOSFET next to the S478 retention
bracket that is at fault.

When you plug the ATX 20 pin connector back in, make sure
the retention tab snaps into place, so you know the
connector is fully seated. If the connector pins get
burned, by having the connector not fully seated, you'll
have no end of problems with power on the board.

HTH,
Paul
 
There are three fan headers. The CPU fan header is fed by a
transistor, and the transistor is controlled by Q-fan. The
other two fan headers are "dumb", and as far as I know, they
are fed directly from the single +12V pin on the ATX 20 pin
connector. (I checked this on my P4C800-E, by using
an ohmmeter, and I got zero ohms when measuring from the +12V
pin on the 20 pin power connector, to the +12V pin on the fan
header.)

The first thing to check, is unplug the computer from the
wall, then unplug the ATX 20 pin connector, and examine it
for damage. See if any of the plastic is melted or there are
burn marks. If everything looks OK, you could measure with
your ohmmeter, from the +12V pin on the ATX 20 pin, over
to the fan header, and see if the copper track on the
motherboard is still in one piece or not. For example, if
you shorted a fan header accidently, enough current would
flow from the ATX 20 pin power connector, to burn out the
fan header copper track. I've never seen a picture of a fuse
on the motherboard, for the fan headers.

If your CPU fan header fails, that is a different story,
as then it could be the MOSFET next to the S478 retention
bracket that is at fault.
Click to expand...

Thank You, Paul.
Fan header test fails, I think Mosfet is fault.
 
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