iMac 27 LCD Data Cable Broken/Fan

Discussion in 'iMac' started by Knocka, Dec 9, 2011.

  1. Knocka macrumors newbie

    Joined:
    Mar 1, 2008
    #1
    I have a 2011 27" iMac i5. I tried to install an SSD (along with the 1TB HD).

    Two problems:

    1. Somehow, when replacing the LCD, the LCD Data Cable (part number 593-1352) got damaged beyond repair and cannot be used. I therefore need a replacement cable ASAP. I am in northern NJ. Any suggestions on where the part can be purchased. I cannot find it for sale anywhere on the internet.

    2. I put the iMac back together (just left the glass off). Connected everything except the broken LCD cable. When iMac boots up, the fan spins FAST and LOUD. I can acess the computer using Log Me In and everything is working properly and disk utility sees the SSD (although I have not formatted it yet.

    What could be causing the fan to spin. I tried pulling the cable out of the SSD (but left it plugged into motherboard and also tried unplugging the DVD. The Fan keeps spinning full speed, even without these two devices connected (although the cable are connected to the motherboard.

    I am wondering if NOT connecting the LCD Cable could, by itself, cause the Fan problem.

    I appreciate the help.
     
  2. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #2
    The fans are in fail safe mode, because they cannot sense the temperature of the hard drive.
     
  3. FrankHahn macrumors 6502a

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    May 17, 2011
  4. Knocka thread starter macrumors newbie

    Joined:
    Mar 1, 2008
    #4
    I am not sure why that would be. I left the original HDD in place. I just ADDED and SSD following instructions that have been recommended here.

    The ONLY cable not connected is the LCD cable (because it is damaged). Would that LCD cable cause the fans to spin this way?
     
  5. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #5
    The LCD cable may be causing a temperature sensor on/in the LCD to not be registered or the SSD isn't providing correct temperature readings.
     
  6. Knocka thread starter macrumors newbie

    Joined:
    Mar 1, 2008
    #6
    I actually tried removing the SSD and trying it and the fan still was at max. So I am thinking it must be related to the LCD cable not being connected. I really have no way to test it further until I receive a new LCD Cable and get it plugged in.
     
  7. MatthewAMEL macrumors 6502

    MatthewAMEL

    Joined:
    Oct 23, 2007
    Location:
    Orlando, FL
    #7
    You need the Optical Temp Sensor Cable in addition to your broken LCD cable.

    www.macpartsonline.com has everything I have ever searched for.

    Your SSD doesn't generate enough heat to worry about, but when the SMC in the iMac is missing ANY temp parameter, it ramps the fans up to 5000RPM and they stay there.

    Good luck.
     
  8. spotts78 macrumors newbie

    Joined:
    Aug 23, 2012
    #8
    I know this is an old thread, but I'm currently in the exact same boat! Did you find a replacement cable and resolve in fan running full speed issue?


     
  9. omvs macrumors 6502

    Joined:
    May 15, 2011
    #9
    I broke my LCD cable last week, and it the fan speed problem. I've got a current workaround using the smc command from the smcFanControl.app that I can share if you're interested (it forces fan speed on the cpu and optical fans, leaves the hard drive fan in automatic mode)

    My new data cable was supposed to arrive today, but probably won't have until the weekend. (apple store said they wouldn't sell me spare part directly). I expect it will resolve the issue though

    (whoops - didn't mean to bump a dead thread... thought the last reply was recent. lol)
     
  10. dckcentaur macrumors member

    Joined:
    Jul 11, 2008
    #10

    I would love that command . I have a bad lcd power connector on my iMac and using a external display for now and the fans are driving me crazy LOL please let me know how I can obtain it.

    Thanks
     
  11. Intell macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #11
    This is a good starting point for limiting ones fan speed with smcFanControl: http://hints.macworld.com/article.php?story=20110704054835249 Just remember, you do so at your own risk and never limite them lower than Apple's idle default.
     
  12. omvs macrumors 6502

    Joined:
    May 15, 2011
    #12
    Okay, first you need SMCfancontroll.app - you can get it from here: http://www.eidac.de. I believe you can use that to directly control the fans if you want, but I'm a bit of an old school unix person, so I did it command line. Here's the details if you're comfortable with Terminal and such:

    You need to extract out the smc command and stash it somewhere - I put it in roots home directory at /var/root. Then wrote a script which does this:

    new-host-2:~ dhartman$ cat resetfans
    /var/root/smc -k 'FS! ' -w 0007
    /var/root/smc -k 'F0Tg' -w 1800
    /var/root/smc -k 'F1Tg' -w 1800
    /var/root/smc -k 'F2Tg' -w 1800

    The script needs to run as root, so you'll want to chmod 755 it, then sudo resetfans to run.

    The first command sets all three fans into into manual control mode. Then the others explicitly set each fan - I believe 1800 gives ~ 1500RPM. The numbers are hex, and 1000 is about 1k rpm, so 1800 is 1.5k, 2000 is 2k, 2800 is 2.5k, etc. If you're gaming, you might want to set the fans somewhat higher - 2-2.5k would be my suggestion.

    Then because I hated giving the command every time I booted, I put the script in roots crontab table to run every minute:

    new-host-2:~ root# crontab -l
    * * * * * /Users/dhartman/resetfans

    NOTE: The SMC also gets reset coming out of sleep, so by having the script run every minute, it'll fix it soon after the machine wakes up.


    If all this is a bit intimidating, PM me with your email address and I'll see if I can put together a zip file with the script all set up that you can hopefully just click on, though that'll require a bit more screwing around on my side.

    NOTE: I replaced my cable a while back (thankfully), so haven't been using it since - but I did test and the script is still working.


    One last thing - I believe the video runs in degraded mode when the sensors aren't working --i definitely got a crappier framerate until the cable got fixed.
     
  13. dckcentaur macrumors member

    Joined:
    Jul 11, 2008
    #13


    Thanks I will try to attempt this weekend . Im new to command but catching on. I will let you know how it went.

    Its my Logic board a blown comp. right at the display power not sure what happened I read a few others having same issue one of those weird apple quirky things if you don't do something just right. its not like I can put the connector on the wrong way it only goes on one way. Well I have a call into someone who fixes comp nets on apple logic boards he swaps out chips so hopefully he will do inexpensively as a replacement logic board (USED)is well over 400 .


    Thanks
     
  14. omvs macrumors 6502

    Joined:
    May 15, 2011
    #14
    Good luck! And remember to up the fans if the temps get too high - if you don't, the system might do a thermal shutdown. Happened twice to me yesterday while gaming, and I finally realized I had left the script automatically running after testing it on Monday. I almost wrote a script to auto-adjust the fans based on functioning sensors, but fixed the data cable before it arrived.

    BTW: You could leave the CPU fan in automatic mode, which might be safer if you run some cpu intensive stuff. I think the LCD cable affects the HDD and ODD fans, which I think were fan 0 and fan. If you only want to force in a subset of fans, you set 'FS! ' to a smaller value. Basically the sum of 1 (fan 0), 2 (fan 1), and 4 (fan2), so 3 in this case.
     
  15. omvs macrumors 6502

    Joined:
    May 15, 2011
    #15
    Actually, this GUI looks pretty good - appears you can slave the fans to a specific sensor. So you could program the ODD to follow the GPU, HDD to the hard drive, and leave the cpu as default. It even has a windows version...

    http://www.crystalidea.com/macs-fan-control
     

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