CPU fan dead .. cant access bios

Hello experts,

I have a system that reports that the processor fan is not working and turns itself off after 5 seconds. I installed a new fan which also would not run when plugged into mainboard. I tried two different places.

I then connected fan directly to power source and the fan runs ok. I guess i need to access the bios in order to switch off the fan monitor function but how can i do this ?? If the 5 volt  rail is dead what can i do?
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d3xt3rAsked:
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PUNKYCommented:
You can do that only bios has its option, some bios does not have it. If your motherboard bios does not have that, you might have problem. Have you tried reset bios after replace the fan? remove coin shape battery on board for 10 minutes will help.
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d3xt3rAuthor Commented:
Thanks. The fact that i get the message of a failed fan implies that the bios does have this monitoring function. I have reset the bios by jumper which changed nothing. The fan monitor is no doubt enabled by default. I am thinking unless i can repair the 5 volt rail i am out o luck.
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PUNKYCommented:
Likely system board is failing. Can you get in bios? what is motherboard brand/model?
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d3xt3rAuthor Commented:
Unable to access bios due to system shutting down after 5 seconds.

Unable to see model of mobo anywhere. Very frustrating because my next step is to replace board with a compatible alternative. Can anyone explain how to find the model of mainboard? Anything to search for?
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willcompCommented:
First, what is make/model of PC?  If it's a home brewed one, look for silk screened manufacturer name and model.  Common locations are between PCI slots and adjacent to memory slots.
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d3xt3rAuthor Commented:
hp pavilion 8802. I can't find any I.D on the motherboard itself however the back of the case has a HP support number, serial number and system number.

As i understand it (with my limited knowledge) if i can't access the bios to disable fan monitor then there is not alot i can do short of replacing mainboard components. If i can acquire the board model i can at least start looking for a replacement.

I know the processor is AMD and the RAM is pc133 sdram. Thnx for everyones help.
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PUNKYCommented:
Link beow is how-to access bios in HP computer:

http://h10025.www1.hp.com/ewfrf/wc/document?docname=bph07110&lc=en&cc=us&dlc=en&product=60726&rule=7472&lang=en

Also I found that there is no option to turn off warning of the cpu fan there:

http://h10025.www1.hp.com/ewfrf/wc/document?docname=bph07110&lc=en&cc=us&dlc=en&product=60726&rule=7472&lang=en

You might try reset bios see if it helps.
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willcompCommented:
As best I can determine, your PC has a Trigem manufactured mobo.  Here's a link to HP documentation for their "SantaFe" mobo.  See if yours is the same (picture towards bottom of web page).

http://h10025.www1.hp.com/ewfrf/wc/genericDocument?lc=en&cc=us&docname=bph07900

Mobo can be replaced with a Socket A uATX mobo that supports 200MHz FSB CPUs and SDRAM.  They are getting hard to chase down now.  This is one option and I have used a couple as replacements.  I don't normally recommend PCChips mobos, but sometimes you have to just take what's available.

http://cgi.ebay.com/PC-Chips-M810LMR-Socket-A-Motherboard-w-Video-SDRAM-LAN_W0QQitemZ120103173992QQcategoryZ31496QQrdZ1QQcmdZViewItem

You will need some expertise to install.  Front audio won't connect and wires will have to be re-arranged in front panel connector block.

Also, would not recommend buying a used SantaFe mobo.  They were manufactured with faulty capacitors.  Take a look at capacitors on your mobo.  Check for swelling of tops (should be flat) and electrolyte leakage.
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d3xt3rAuthor Commented:
Punky
Thanks for the help. Please read the original question thoroughly. I can NOT get into the bios. Not because i don't know how but because the CPU thinks its overheating.

Willcomp .... yes thats the offending board, or very similiar. So i need Socket A uATX. I'll check the capacitors later, if i can get away with replacing one i will be happy. Thanks for the info ... very helpful.
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MarkCommented:
Does the replacement fan have a three wire plug. This type of CPU fan has speed indication.The bios error you are recieving depends on sensing the speed of the fan through the onboard CPU FAN connector. You can't use just any plug on the board , just the one that is specified for the CPU fan.
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d3xt3rAuthor Commented:
Thanks sparkmaker, yes it is 3 wires. I realize the fan monitor is only available through the cpu fan input,  i tried another fan input just to try to get power to it. Now it is wired directly to PSU and works ok which is great, but doesn't get me around the error and shutdown.

Capacitors all look OK at a glance. Without any other solution to getting around this fan monitor setting in the bios i am looking at replacing the mainboard.
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MarkCommented:
It may be possible to use the tachometric signal wire from the fan on the CPU fan header to fool the motherboard into thinking there is a fan running. You would need to pull the +12v and ground from the fan and connect it directly to the PSU as you have now but also connect the Tach signal to the CPU fan connector.  Here is the pinout. Ensure the proper orientation  of the clip  when doing this to get the right wire. http://www.pcdoctor-guide.com/wordpress/images/cpufanpinoutlabeled.jpg
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d3xt3rAuthor Commented:
You little ripper!  Thanks sparkmaker.

Worked a treat. I was able to access the bios using this tacho diversion method.
Kudos to you for thinking outside the box.
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willcompCommented:
Way to go Sparky!!  After first reading your response, it was one of those "why didn't I think of that" minutes.  I'll file that for future reference.
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MarkCommented:
Thanks d3xt3r. Where I  work, sometimes "outside the box" is all you have. I just glad you didn't call me a BIG ripper ;-)
@willcomp-->I was doing a bit of a LURK on this one as I have seen the Trigem be a real  pain. Just a eureka moment for me actually. I was at work,(night shift) brainstorming on another project with a friend(who happens to be a Medical Doctor and a Mechanical Engineer) and the creative juices must have been flowing. Ditto on the reference.
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