MacBook Pro Fan on full when using AC

Discussion in 'MacBook Pro' started by kolax, Jul 30, 2008.

  1. kolax macrumors G3

    kolax

    Joined:
    Mar 20, 2007
    #1
    Okay, my MacBook Pro fans will come on full blast (or close to) even though I am doing very little when connected to AC from anything between 10 minutes and an hour. If I unplug it, after about 15 seconds the fans die down and the laptop is silent.

    I've looked at a few other various threads and there isn't a definite solution or cause.

    What gives?
     
  2. Bobioden macrumors 68000

    Bobioden

    Joined:
    Sep 23, 2007
    Location:
    Denver
    #2

    My MBP always runs hotter when plugged in and using it.
     
  3. digitalpencil macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #3
    mine's been overheating a lot lately although i'm getting the opposite problem, my fans don't seem to kick in at all.. :(
    what temps are you getting out of curiosity? can you post your istat?
     
  4. mchank macrumors regular

    Joined:
    Feb 26, 2006
    #4
    My Macbook Pro does this when I'm recharging and the battery is below 50%. I've read that this is due to the memory controller heating up when when the laptop is being recharged. My fans jump up to ~4000rpms and go back down to normal (2000rpm) after 30 mins or so.
     
  5. kolax thread starter macrumors G3

    kolax

    Joined:
    Mar 20, 2007
    #5
    Average temperature while just surfing the net is about 63'C.

    Last week, a friend of mine bought a new MacBook and asked me to help set it up. While installing bits and bobs, the fan came on and I could actually feel the air flowing out the back! With my MBP, the air flow coming out of the back isn't much even when both fans are at 6000rpm. Also, the fan was a lot quieter in the MacBook (even when running full blast), compared to the two in my MacBook Pro.

    The fans sounds like a jet engine as soon as it goes above 3000rpm in my MBP!
     
  6. kolax thread starter macrumors G3

    kolax

    Joined:
    Mar 20, 2007
    #6
    Here's a screenshot of iStat showing my temperatures, CPU usage and fan speeds.

    Every time I plug in the AC, after a couple of minutes the fans will go to 6000rpm and it makes a hell of a noise.

    [​IMG]
     
  7. digitalpencil macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #7
    6000rpm is a hell of a speed! If the airflow isn't that strong i'd wager the inlets/exhausts are partially blocked which is probably why the fans speed up so high (especially when plugged in as your cpu will run on a higher voltage) Probably a good idea to take apart and clean with compressed air.. just ensure you're moving any dust etc. out of the machine rather than in! Check out the ifixit fan guides for how to get in and clean.
     
  8. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
  9. kolax thread starter macrumors G3

    kolax

    Joined:
    Mar 20, 2007
    #9
    Interesting - do you mean actually taking my MBP apart?

    Yes - I also did a complete reinstall a few days ago, and the problem persists.

    I'm sure it is a ventilation issue - the bottom of my MBP gets very hot, even when the CPU usage is at about 10%.
     
  10. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #10
    But your temperatures aren't that high.
     
  11. kolax thread starter macrumors G3

    kolax

    Joined:
    Mar 20, 2007
    #11
    Temperatures vary.

    The case is pretty hot right now, and these are the stats:

    [​IMG]

    This is what confuses me - the temperatures are higher than the previous screenshot, yet the fans are idle and I'm on AC.
     
  12. digitalpencil macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #12
    if you've done a complete reinstall and the problem still persists i'd think the issue would have to be hardware related and most probably attributed to poor ventilation.. my thinking was that when you're plugged in, the CPU voltage will change, resulting in more heat, triggering the fan which, due to intake blockages, will carry on accelerating exponentially as it's not effectively cooling the CPU.. i could be wrong though, it might be a busted temp gauge but that sounds highly doubtful..
    i'd whip off the lid and poke around inside but that's just me.. :D
    you'll have to remove the upper case and unscrew the fan housing on either side, once disconnected you clean the fan itself and clean out the intakes. put it all back together again and see if the problem persists.
    see: http://www.ifixit.com/Guide/Mac/MacBook-Pro-15-Inch-Core-2-Duo/Right-Fan/115/18/Page-6/Right-Fan
     
  13. kolax thread starter macrumors G3

    kolax

    Joined:
    Mar 20, 2007
    #13
    I'm currently syncing my iDisk and the fans have come on full blast. Even though the CPU usage is at 15% and the temperatures are well below when fans would come on full blast on battery mode.

    Same happens when MobileMe syncs everything else, fans come on full blast even though there isn't really much heat.

    This is really frustrating - I know this is a very powerful laptop, but it really pisses me off that I'm barely doing anything and the fans are on full blast making a racket. I was going to take it to Cancom but it will be 7-10 days just for them to check the insides.

    A question for anyone else with a MacBook Pro - when the fans are on full blast, can you feel air actually coming out of the exhaust at the back, or is it very faint? My mates MacBook is like a hand dryer, the hot hair really gets pushed out of the exhaust, and the fans are also a lot lot quieter.

    [​IMG]
     
  14. pinktank macrumors 6502

    Joined:
    Apr 5, 2005
    #14
    this happened to my cousin, he did a pram reset and it was all well, he uses smcfancontrol now
     
  15. Consultant macrumors G5

    Consultant

    Joined:
    Jun 27, 2007
    #15
    Look at the left side of your CPU usage history.
    Your CPU just finished doing something with high CPU usage.

    high CPU usage -> high CPU temperature -> high rpm fans attempting to cool down

    Play a lot of flash videos or go on sites with a lot of flash?
     
  16. kolax thread starter macrumors G3

    kolax

    Joined:
    Mar 20, 2007
    #16
    I've reset PRAM and SMC - and SMC Fan Control only lets you choose the minimum speed - I have trouble with the fan going full blast, not coming on at all!

    I've also used Fan Control, but OS X seemed to ignore the settings I used at certain times.
     

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