CPU Fan problem

[Antares 531]

I have an older desktop computer that I built a few years back. I'm
still running Windows XP Pro SP3 on this computer. It has a Gigabyte
GA-P35-DS3L motherboard with an Intel Core 2 Duo 2.66 GHz CPU setup.
This computer has two Western Digital WD5000 hard drives and both have
about half the drive space available.

This computer has worked very well over the years but recently, the
CPU fan will do a start - stop - start - stop over and over again when
I try to start this computer up or bring it out of hibernate. When
this occurs there is a loud beep that is synchronized with the CPU
fan's on again, off again pattern. I can remove the side cover of this
computer and use my finger to twirl the CPU fan when it stalls out.
This usually gets it going and all is well until the next time I start
this computer.

Is this a failing CPU fan or is it a motherboard fan control circuit
failure?

Any time I put my finger on the fan and stop it the same beep pattern
occurs. Then, if I twirl the fan and get it going the beeping stops.

Thanks for any suggestions. I can go buy a new fan if this seems the
most likely source of the problem, but I don't know about trying to
repair or replace the motherboard. Gordon

 

[PA Bear [MS MVP]]

Is this a failing CPU fan or is it a motherboard fan control circuit
failure?

It is something you should ask here:

microsoft.public.windowsxp.hardware

<http://groups.google.com/group/microsoft.public.windowsxp.hardware/topics?lnk=srg&hl=en>

 

[Antares 531]

I have an older desktop computer that I built a few years back. I'm
still running Windows XP Pro SP3 on this computer. It has a Gigabyte
GA-P35-DS3L motherboard with an Intel Core 2 Duo 2.66 GHz CPU setup.
This computer has two Western Digital WD5000 hard drives and both have
about half the drive space available.

This computer has worked very well over the years but recently, the
CPU fan will do a start - stop - start - stop over and over again when
I try to start this computer up or bring it out of hibernate. When
this occurs there is a loud beep that is synchronized with the CPU
fan's on again, off again pattern. I can remove the side cover of this
computer and use my finger to twirl the CPU fan when it stalls out.
This usually gets it going and all is well until the next time I start
this computer.

Is this a failing CPU fan or is it a motherboard fan control circuit
failure?

Any time I put my finger on the fan and stop it the same beep pattern
occurs. Then, if I twirl the fan and get it going the beeping stops.

Thanks for any suggestions. I can go buy a new fan if this seems the
most likely source of the problem, but I don't know about trying to
repair or replace the motherboard. Gordon

I disconnected the CPU fan from the marked CPU Fan power connection
and connected it to one of the extra cooling fan power connections on
the motherboard. When I started the computer, the fan operated
smoothly and without any interruptions, but the beeping came on and
didn't stop until I shut the computer down and moved the CPU fan
connector back to its intended place.

Also, I notice that if I put my finger in the CPU fan when the boot
process is under way and keep the fan from starting, briefly, then
remove my finger and let it run, all goes well. That is, the beeping
stops and the fan starts running smoothly.

The fact that the fan will run smoothly, without interruption, when
connected to this other power connection suggests that the fan is not
at fault. I'm guessing there is some temperature sensor associated
with the CPU that is sending bad signals to the fan controller.

Comments??? Gordon

 

[Paul in Houston TX]

I have an older desktop computer that I built a few years back. I'm
still running Windows XP Pro SP3 on this computer. It has a Gigabyte
GA-P35-DS3L motherboard with an Intel Core 2 Duo 2.66 GHz CPU setup.
This computer has two Western Digital WD5000 hard drives and both have
about half the drive space available.

This computer has worked very well over the years but recently, the
CPU fan will do a start - stop - start - stop over and over again when
I try to start this computer up or bring it out of hibernate. When
this occurs there is a loud beep that is synchronized with the CPU
fan's on again, off again pattern. I can remove the side cover of this
computer and use my finger to twirl the CPU fan when it stalls out.
This usually gets it going and all is well until the next time I start
this computer.

Is this a failing CPU fan or is it a motherboard fan control circuit
failure?

Any time I put my finger on the fan and stop it the same beep pattern
occurs. Then, if I twirl the fan and get it going the beeping stops.

Thanks for any suggestions. I can go buy a new fan if this seems the
most likely source of the problem, but I don't know about trying to
repair or replace the motherboard. Gordon

Fan is shot. Get a new one before the cpu is destroyed.

 

[Paul]

I have an older desktop computer that I built a few years back. I'm
still running Windows XP Pro SP3 on this computer. It has a Gigabyte
GA-P35-DS3L motherboard with an Intel Core 2 Duo 2.66 GHz CPU setup.
This computer has two Western Digital WD5000 hard drives and both have
about half the drive space available.

This computer has worked very well over the years but recently, the
CPU fan will do a start - stop - start - stop over and over again when
I try to start this computer up or bring it out of hibernate. When
this occurs there is a loud beep that is synchronized with the CPU
fan's on again, off again pattern. I can remove the side cover of this
computer and use my finger to twirl the CPU fan when it stalls out.
This usually gets it going and all is well until the next time I start
this computer.

Is this a failing CPU fan or is it a motherboard fan control circuit
failure?

Any time I put my finger on the fan and stop it the same beep pattern
occurs. Then, if I twirl the fan and get it going the beeping stops.

Thanks for any suggestions. I can go buy a new fan if this seems the
most likely source of the problem, but I don't know about trying to
repair or replace the motherboard. Gordon

Based on your description, I'd say the BIOS is detecting the low
fan speed, and the "beep" is a cry for help.

Fans are controlled two ways. The old way, was a three wire fan, with
voltage control on the +12V lead to the fan. If the +12V copper track
gets burned, or if there is a transistor near the header that
is bad, that can cause the fan to run slow. Accumulated
dirt can also cause the fan to run slow.

The new control method, uses a four wire tiny connector, with the
supply voltage lead sent a fixed +12V signal, and the new fourth wire
carrying a PWM (pulse width modulation) signal. If the PWM signal is
disconnected, it floats to a logic 1 on the fan end, and that causes
the fan to run at 100% speed. A PWM controlled fan can run slow,
if the +12V copper track gets burned (as before), or if the PWM signal
is grounded, that would indicate a request for "low speed". And the low
speed, may be too slow for the BIOS speed check. The PWM signal would
have a 25KHz 50% duty cycle square wave on it, if the motherboard
wanted the fan to run at 50% speed (half way).

The best way to handle this, is to bypass the CPU fan header. But
there is a problem with this approach. You can get an adapter
cable which is included in the box some cooling fans come in.
The last "Vantec Stealth" fan I bought, has a cable with
a male Molex 4 pin, a female Molex 4 pin (for daisy chaining
connectors(, and an LP3 male to connect to a fan. The fan spins fine
using one of those (you can connect an LP3 to a four pin Intel
fan, as the fourth PWM pins floats and that signals a request
for 100% speed).

What's wrong when you do that, is while the CPU is now cooled
properly, the motherboard CPU fan header has nothing connected to
it. The BIOS expects to see thirty pulses per second
on the tachometer pin of the CPU fan header. You then need to
run a wire, from the adapter cable, to the CPU fan header.

I own precisely one of these adapter cables which was designed
to do exactly that, and you can't normally just buy them at
the store. If I needed a second one now, I'd have to custom
make it from parts. Luckily, my local electronics store
(active123.com) carries male and female LP3 connectors,
so I have all the parts I need.

LP3 male
Moles_male -----+--------------> +12V --- connect
+12,GND,GND,+5 | --------> GND --- to Intel CPU
| +-------- Tachometer --- four pin fan
Molex_female ---+ | ----/ (PWM floats)
+12,GND,GND,+5 |
+--------> LP3 female --- Plug onto
/--- (plug onto --- motherboard CPU
/--- --- fan header
----/ (PWM is no connect)

The adapter cable in this case, comes with four connectors. Two
Molex disk drive connectors are provided, so you can "daisy
chain" power and steal power from a hard drive connector, without
"using up" any ATX power supply connectors.

One LP3 connector goes to the Intel CPU fan. It is a three pin
male connector, with alignment tab to prevent wrong insertion.
The Intel four pin CPU fan connects to this, and the fourth (PWM)
pin on the Intel fan is not connected. This causes the Intel
fan to run at 100%, giving good cooling to the CPU.

The second LP3 connector is a female. It has only one wire on
it, and the other two holes are blank. You plug that three pin
female, into the motherboard four pin (LP4) CPU fan header. The PWM
pin doesn't need a connection (it's an output from the motherboard,
which in this case isn't being used). There is a grand total
of only one signal being connected via this LP3 female. And
that is the tachometer or RPM signal, flowing from the Intel fan
to the motherboard header. That RPM signal is needed to fool
the BIOS into thinking the CPU fan header is normally
connected.

My local electronics store, carries LP3 connectors and crimp
pins, so I can make an adapter of that type. I could, for example
buy a Vantec Stealth fan for $12.77 at a local computer store,
buy a single wire and add an LP3 female to the
cable assembly, to make a complete cable assembly
to bypass the power coming from the motherboard CPU
fan header. By connecting the LP3 female with the RPM
pulse signal on it, to the CPU fan header, that keeps
the BIOS convinced all is well with the fan.

By bypassing the CPU fan header that way, my hope would
be that the fan can be properly powered and run at
full speed. There would then be no need to turn it
with your finger to get it started.

Don't forget to check the BIOS fan settings, in case
you've selected some fancy automated control. Set it
to manual mode, in such a way as to request 100% CPU
fan speed at all times. That will give the fan the best
chance of working properly for you. I don't normally
use the built-in speed controls on the motherboards -
if I need to slow down a CPU fan, I use an external
adapter for that.

*******

There is one other explanation for this problem. It
has nothing to do with the fan, and has to do with
the motherboard design itself. You need to find some
reviews for the motherboard, to see if other users
have experienced this problem as a motherboard failure.
If the motherboard is bad, then bypassing the CPU fan header
won't be enough to fix it.

One of the reviews on the Newegg site, notes that
the CPU fan doesn't start to spin right away. That
is probably the PWM signal, not being set to a
high enough duty cycle by the BIOS. Apparently,
when the CPU gets warm enough, the fan then starts
to spin. But that's not the other kind of problem,
which appeared to be a design problem with the
motherboard. And in the Newegg reviews, I can't find
any examples of that kind of failure. So your
symptoms probably aren't a motherboard design issue,
as I don't see any examples on Newegg like that.

http://www.newegg.com/Product/Product.aspx?Item=13-128-059

HTH,
Paul

 

[BillyBob]

HTH,
Paul

Geez,

Didn't think you would need an electrical engineer to fix a cpu fan.
Wouldn't it just be easier to buy a new fan ? You can get an el cheapo for
under $20. If it solves the problem, then voila! If it doesn't then it
certainly rules out the fan as the problem and now you have a spare fan for
future use. If nothing more, it can be used for diagnostic purposes.

BB

 

[Tester]

Based on experience.

Does your experience also extends to making sure the time on your system
is automatically synchronized to ensure it is not out by more than a minute?

 

[Paul in Houston TX]

Based on what? What makes you assume it's the fan itself, and not its
control circuitry?

Based on experience.

 

[Paul in Houston TX]

Does your experience also extends to making sure the time on your system
is automatically synchronized to ensure it is not out by more than a
minute?

Nah, I let time.nist.gov take care of that.

 

[Paul]

Geez,

Didn't think you would need an electrical engineer to fix a cpu fan.
Wouldn't it just be easier to buy a new fan ? You can get an el cheapo
for under $20. If it solves the problem, then voila! If it doesn't
then it certainly rules out the fan as the problem and now you have a
spare fan for future use. If nothing more, it can be used for
diagnostic purposes.

BB

You've missed the point. If the motherboard fan power distribution
is damaged, my solution bypasses the damage. Buying a new CPU fan,
won't repair a damaged motherboard. Using a Molex to LP3 adapter
cable, with separate LP3 for tacho signal, eliminates any power
draw from the CPU fan header. It's a debugging aid, to see if the
problem is motherboard power.

Paul

 

[Paul]

I disconnected the CPU fan from the marked CPU Fan power connection
and connected it to one of the extra cooling fan power connections on
the motherboard. When I started the computer, the fan operated
smoothly and without any interruptions, but the beeping came on and
didn't stop until I shut the computer down and moved the CPU fan
connector back to its intended place.

Also, I notice that if I put my finger in the CPU fan when the boot
process is under way and keep the fan from starting, briefly, then
remove my finger and let it run, all goes well. That is, the beeping
stops and the fan starts running smoothly.

The fact that the fan will run smoothly, without interruption, when
connected to this other power connection suggests that the fan is not
at fault. I'm guessing there is some temperature sensor associated
with the CPU that is sending bad signals to the fan controller.

Comments??? Gordon

If you

1) Connected CPU fan to Aux fan header to give the fan power.

2) Ran a tachometer signal from the CPU fan, back to the CPU fan
header RPM pin, the beeping would stop.

And that is basically the function of the adapter cable I explained
in my other post. To avoid any kinds of issues related to problems
with CPU fan header power or control.

Sometimes this problem is a control issue, where the BIOS "auto" fan
control isn't working properly, and the fan doesn't spin. If you find
another way to power the fan, and also find a way to put a valid
RPM signal onto the CPU fan header, all problems would be solved.

Another way to fix it, is set the BIOS fan control to "Manual" or
equivalent. But some BIOS are so brain-dead, they even screw that up.

Paul

 

[Antares 531]

I disconnected the CPU fan from the marked CPU Fan power connection
and connected it to one of the extra cooling fan power connections on
the motherboard. When I started the computer, the fan operated
smoothly and without any interruptions, but the beeping came on and
didn't stop until I shut the computer down and moved the CPU fan
connector back to its intended place.

Also, I notice that if I put my finger in the CPU fan when the boot
process is under way and keep the fan from starting, briefly, then
remove my finger and let it run, all goes well. That is, the beeping
stops and the fan starts running smoothly.

The fact that the fan will run smoothly, without interruption, when
connected to this other power connection suggests that the fan is not
at fault. I'm guessing there is some temperature sensor associated
with the CPU that is sending bad signals to the fan controller.

Comments??? Gordon

Thanks for all the information. I got another fan and will install it
as soon as I get some thermal paste. This is the easiest process for
checking out the fan. If the new fan also does the stop and go dance I
will at least know that it isn't the fan. Then I'll probably go ahead
with the suggestion that I power the fan by one of the motherboard's
cooling fan connections, then figure out how to tie the tachometer
signal back to the CPU fan connector on the motherboard.

But, if this CPY tachometer input on the motherboard is malfunctioning
somewhere the problem won't be resolved. I guess if this develops I'll
be looking for a replacement motherboard.

Gordon

 

[Antares 531]

Geez,

Didn't think you would need an electrical engineer to fix a cpu fan.
Wouldn't it just be easier to buy a new fan ? You can get an el cheapo for
under $20. If it solves the problem, then voila! If it doesn't then it
certainly rules out the fan as the problem and now you have a spare fan for
future use. If nothing more, it can be used for diagnostic purposes.

BB

Right, if the problem is indeed within the fan, but if the problem has
its roots in the motherboard's fan control circuitry then replacing
the fan a dozen times would not solve the problem. Gotta test out the
simplest things first, so I'll start with a new fan, then if that
doesn't work I'll probably replace the motherboard.

Gordon

 

[Paul]

Thanks for all the information. I got another fan and will install it
as soon as I get some thermal paste. This is the easiest process for
checking out the fan. If the new fan also does the stop and go dance I
will at least know that it isn't the fan. Then I'll probably go ahead
with the suggestion that I power the fan by one of the motherboard's
cooling fan connections, then figure out how to tie the tachometer
signal back to the CPU fan connector on the motherboard.

But, if this CPY tachometer input on the motherboard is malfunctioning
somewhere the problem won't be resolved. I guess if this develops I'll
be looking for a replacement motherboard.

Gordon

CPU fan options:

CPU_three_pin CPU_four_pin

Pin 1 ground GND GND
Pin 2 power +12V (variable) +12V (fixed)
Pin 3 sense RPM RPM
Pin 4 control PWM (25KHz, 50% duty cycle = 50% fan speed)
(if left floating/unconnected, gives 100%)

If the +12V is failing, that can make the fan run slow. Sometimes,
a copper track carrying +12V gets burned, or a control transistor
gets damaged. (Note - never connect a fan to a motherboard header, with
the power running. One slip while you're installing the connector, can
damage something. Causing the +12V pin to touch the GND pin, ruins
the power distribution track in the motherboard - there is no fuse
protecting it!)

The PWM signal can have control issues (bad BIOS setup). Or, the
signal can be stuck at zero (run fan slow), or stuck at one (run fan fast).
Disconnecting the PWM signal, and letting it float, is the best debug
step there.

The RPM signal is an input to the motherboard. The BIOS monitors RPM,
to detect a stuck fan. Possible responses if no fan pulses are received,
is to "beep" and put up a "press F1" prompt and prevent the system from
booting. Or, the BIOS can turn the PC off, as a precaution. Normally,
the THERMTRIP signal from the processor, covers all manner of cooling
failures for the CPU, and it is most likely to be the reason the
computer shuts off. If your computer shuts off after five seconds, it
could be via the BIOS, or via the purely hardware THERMTRIP feature.

If the RPM (tachometer) signal is not connected to the CPU fan header
(the one most likely to be carefully monitored), then you need some
way to fake it. In some cases, connecting a three wire, case cooling
fan to the CPU fan header, is enough to do it (a three wire fan provides
the fake RPM signal). But if the CPU fan header has a defective +12V feed,
then that won't work, because the alternate fan won't spin either.

That's why the adapter cable I described is a good alternative, because
it covers a few of the fault cases. And as long as you can find a means
to put a "working" RPM pulse signal, onto the CPU fan header, then the
BIOS is going to be happy, and let the system boot.

So using a single wire, and "borrowing" an RPM signal to use, can be
used to keep the CPU fan header "happy".

Connector

Pin 1 ground ---
Pin 2 power ---
Pin 3 sense <--- RPM (from some other fan)
Pin 4 control

In rare instances, yes, it is possible for the sensing function
on the SuperI/O chip to be damaged. I can't remember the last
time that's happened though. It is pretty defensively designed,
so it would take deliberate abuse to ruin it (voltages well outside
normal fan voltages). If you scuffed across your carpeted floor,
and discharged static electricity into Pin 3, do it enough times
and you could probably ruin it.

Paul

 

[Antares 531]

I have an older desktop computer that I built a few years back. I'm
still running Windows XP Pro SP3 on this computer. It has a Gigabyte
GA-P35-DS3L motherboard with an Intel Core 2 Duo 2.66 GHz CPU setup.
This computer has two Western Digital WD5000 hard drives and both have
about half the drive space available.

This computer has worked very well over the years but recently, the
CPU fan will do a start - stop - start - stop over and over again when
I try to start this computer up or bring it out of hibernate. When
this occurs there is a loud beep that is synchronized with the CPU
fan's on again, off again pattern. I can remove the side cover of this
computer and use my finger to twirl the CPU fan when it stalls out.
This usually gets it going and all is well until the next time I start
this computer.

Is this a failing CPU fan or is it a motherboard fan control circuit
failure?

Any time I put my finger on the fan and stop it the same beep pattern
occurs. Then, if I twirl the fan and get it going the beeping stops.

Thanks for any suggestions. I can go buy a new fan if this seems the
most likely source of the problem, but I don't know about trying to
repair or replace the motherboard. Gordon

I got the thermal paste then installed the new fan and powered the
computer up. Same ole same old! The fan will go ahead and operate if I
give it a boost with my finger and get it started. This MUST be a
motherboard problem, however, I'm still hoping someone can tell me
about some BIOS setting or some such that I can change and maybe get
this resolved. This old computer worked very well for several years,
so I doubt this problem is being caused by some BIOS setting error,
but, maybe something "automatic" happened that I don't know about.

This is not a National Emergency. I don't use that old computer very
much, and when I do I can twirl the fan to get it going. And, yes,
I've checked the old and the new fan to make sure they are not clogged
or otherwise obstructed. Both rotate freely and the new one doesn't
have any ling down in the shaft area.

Gordon

 

[glee]

I got the thermal paste then installed the new fan and powered the
computer up. Same ole same old! The fan will go ahead and operate if I
give it a boost with my finger and get it started. This MUST be a
motherboard problem, however, I'm still hoping someone can tell me
about some BIOS setting or some such that I can change and maybe get
this resolved. This old computer worked very well for several years,
so I doubt this problem is being caused by some BIOS setting error,
but, maybe something "automatic" happened that I don't know about.
snip

You can try looking in BIOS Setup for Smart Fan Control or CPU Smart Fan
Function, and if found, write down what it's currently setings are, then
set it to Disabled, save and exit, and see if it has any effect.

On AMI BIOS it is in the PC Health screen, like this:
http://www.overclock.net/amd-motherboards/527002-automatic-cpu-fan-cpu-smart-fan.html

With other BIOS' it may be found in the "CPU," "Advanced," or
"Overclocking" options.

 

[choro]

I got the thermal paste then installed the new fan and powered the
computer up. Same ole same old! The fan will go ahead and operate if I
give it a boost with my finger and get it started. This MUST be a
motherboard problem, however, I'm still hoping someone can tell me
about some BIOS setting or some such that I can change and maybe get
this resolved. This old computer worked very well for several years,
so I doubt this problem is being caused by some BIOS setting error,
but, maybe something "automatic" happened that I don't know about.

This is not a National Emergency. I don't use that old computer very
much, and when I do I can twirl the fan to get it going. And, yes,
I've checked the old and the new fan to make sure they are not clogged
or otherwise obstructed. Both rotate freely and the new one doesn't
have any ling down in the shaft area.

Gordon

Why don'tyou go into BIOS and restore the default settings and try it like
that and see what happens?

 

[BillyBob]

You've missed the point. If the motherboard fan power distribution
is damaged, my solution bypasses the damage. Buying a new CPU fan,
won't repair a damaged motherboard. Using a Molex to LP3 adapter
cable, with separate LP3 for tacho signal, eliminates any power
draw from the CPU fan header. It's a debugging aid, to see if the
problem is motherboard power.

Paul

Paul,

I get your point. Most people would probably agree that it is easier to
debug the fan as the problem than the motherboard as the problem.

It is much easier to buy a $20 fan, unplug the old one and plug in the new
one. If the new fan works then you saved yourself a whole bunch of trouble
(at least for the average Joe) monkeying around with the motherboard. If it
doesn't fix the problem then, in my opinion, it was a well spent $20 to
confirm that it is a MB problem. Versus monkeying around with the MB to
bypass a problem fan.

Antares 531 seems to agree with me. "Gotta test out the simplest things
first, so I'll start with a new fan, then if that doesn't work I'll probably
replace the motherboard." Read the post that follows the one I am
responding to.

BB

 

[Paul in Houston TX]

A little late to the party? (He's already tested another fan, and
as some of us predicted, it wasn't the fan).

You were correct and I was wrong. I thought for sure it was the fan.

 

[BillyBob]

A little late to the party? (He's already tested another fan, and
as some of us predicted, it wasn't the fan).

Bill,

Reread the dialogue between Paul and myself. You misunderstood the context
of my remarks. I read the thread where the Op replaced the fan to no avail.
My comments were directed at Paul whose argument is to fiddle with the MB.
I was simply stating that it is far easier to rule out the fan as the
problem before messing with the MB. Whether that is the case or not in this
instance (which it isn't) wasn't my point.