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Laptop CPU fan not working.


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15 replies to this topic

#1 Wooshie

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Posted 15 February 2012 - 02:10 PM

I received a dell latitude d620 laptop second hand. I was told the cpu fan was bad. I replaced the fan with a brand new unit and nothing. I thought maybe I got bad fan. I tried several other 3 pin fans I had laying around and none would work. I saw no obvious damage to the fan connector or the motherboard. I decided to replace the mobo anyway. I got the new mobo today and got it installed and... no cpu fan again. I doubt I could have 2 mobo's with bad fan connectors. I have looked online and don't find this problem at all. So my question is, Why does my cpu fan not work? I have tested this motherboard with known working 3 pin fans and none of them work.

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#2 caperjac

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Posted 15 February 2012 - 02:15 PM

so the computer works, correct , but the fan doesn't .i say that because the laptop should still boot and work with out a fan ,it would just over heat .most if not all laptop fans only run for a few seconds on bootup ,and will come on when laptop heats up
its possible that the connection to the motherboard has desoldered perhaps and maybe if it is could be re-soldered to make it work

Edited by caperjac, 15 February 2012 - 02:22 PM.

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#3 Wooshie

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Posted 15 February 2012 - 03:52 PM

The laptop does work. I tried resoldering the motherboard the first time with no result. I got a new motherboard and it does the exact same thing. My cpu and motherboard temps sit around 72C. Way to hot. I have checked and verified the fan doesn't come on at all.

#4 James Litten

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Posted 15 February 2012 - 04:34 PM

Is it at all possible for you to try a different power supply? Have you tried it from the battery only?

Often in situations like this the fan is hardwired to another power source on the board (I do not recommend that for a laptop CPU fan) as a workaround. Since it happened to two boards with you, the common denominator seems to be your power source.

Try this program to see if your voltages are correct. It detects stuff well on most laptops and is open source software...

http://openhardwaremonitor.org/

James

#5 Wooshie

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Posted 16 February 2012 - 12:59 PM

It works the same on battery or plugged in. I didnt see any voltage reports. Still way to hot.

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#6 James Litten

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Posted 16 February 2012 - 02:02 PM

I'm afraid your fan power output is dead :(

Like I said, I've seen this before with laptops like this. You can get power to the fan from another system on the board (some use a USB ports power) but the fan will run fast all of the time and it will be risky (laptops are physically engineered to run a very specific way) so don't use it for anything you can't afford to lose.

It might be a component like a capacitor in the circuit that provides power to the fan jack but most likely it is a solder or trace problem that would be difficult to find let alone repair.

Wish I had better news.

Now, I could be wrong and you should always get a second opinion. Especially when the first opinion is from a stranger on an internet forum :)

James

EDIT: I forgot you tried two motherboards. Is there a separate power board? If so, then that's your problem. I would not expect to see this on two mobos in a row.

EDIT 2: I checked the service manual and I must be misunderstanding you. You have two motherboards and a fan that you have verified works. The fan does not work on either board regardless of being run from the battery or the AC adapter? I'm sorry, it does not make sense to me. I guess you should disregard any advice I've given :(

Edited by NeverSayDie, 16 February 2012 - 02:13 PM.


#7 Wooshie

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Posted 16 February 2012 - 08:26 PM

Lol. The second edit is correct. It does have a daughterboard with usb ports on it. It is not anywhere near the fan. Someone I know said I should try updating the BIOS. Another piece of advice was to replace with a Dell fan and not the generic unit I purchased online. I work on a LOT of laptops and I am used to making motherboard repairs.(reflow, reball, solder,) I just cant identify the problem.

#8 caperjac

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Posted 17 February 2012 - 06:05 AM

what about using a multimeter to see if there is any power at the plug socket

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#9 Wooshie

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Posted 17 February 2012 - 11:09 AM

I am going to tear it down again later. What sort of power reading should I see at that socket?

#10 Wooshie

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Posted 17 February 2012 - 02:39 PM

I have tested with a multi meter and I am getting good power from the fan connector socket. I am going to order a replacement fan from dell. I will post if this solves my problem.

#11 caperjac

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Posted 17 February 2012 - 05:40 PM

knowing Dell they have something in the bios to detect through the 3rd wire and tell it not a dell fan ,something like there do with there power supply /chargers .
good luck ,hope it woks for you

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#12 Wooshie

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Posted 23 February 2012 - 09:10 PM

Bios update to A10 and dell fan has fixed the problem.

#13 caperjac

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Posted 24 February 2012 - 05:26 AM

great to see you got it fixed

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#14 MrAmazing41086

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Posted 27 February 2012 - 09:23 AM

I have a Dell Inspiron. My fan stopped working even when it booted up so I replaced it... The new fan worked but then the fan stopped working.. I would like to know is there something I should do before buying a new fan?

#15 mrmox2

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Posted 05 September 2013 - 06:24 PM

Bios update to A10 fixed same issue for me

thx






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