2011 iMac Ambient Temperature Sensor failure after installing another drive

Discussion in 'iMac' started by Gurpartap Singh, Feb 25, 2014.

  1. Gurpartap Singh macrumors newbie

    Jun 9, 2010

    I performed the Dual Hard Drive Kit upgrade as suggested in the guide at http://www.ifixit.com/Guide/Installing+iMac+Intel+27-Inch+EMC+2429+Dual+Hard+Drive+Kit/7575

    I followed the steps precisely during the whole process.

    After the second drive (SSD) was installed, I booted up the iMac and heard loud fan noise after a few seconds. Both CPU and ODD fans are running at full speed.

    I have tried resetting SMC/PRAM, but to no avail. I reassembled the logic board twice, with and without the Dual Drive Kit upgrade. It still didn't fix the problem.

    I have also noticed that it is not just the fans that are loud, my game which I play every day at 30fps, is crawling at 6-7fps after the upgrade (still utilizing the HDD though, not the SSD).

    Running the Apple Hardware Test revealed failure with TA0P code, which indicates Ambient Temperature sensor/connector failure according to some google search results.

    Moreover, Temperature Gauge Pro app reports the following:

    Some further Googling has revealed that this person had a similar problem and flipping the LCD Thermal Sensor Cable fixed it for him: http://forums.macrumors.com/showpost.php?p=16423197&postcount=13

    However, I removed the LCD panel from the iMac and booted it with external Cinema Display. The fans are still loud. So I doubt that the problem is with LCD sensor for me. Maybe I should pay attention to the Ambient Sensor/connector, since the AHT failure also reported a fault with that.

    Another thread mentions a similar problem, but doesn't include any solution: http://forums.macrumors.com/showthread.php?t=1669643

    Any help would be appreciated on how to approach at fixing this Ambient Temperature Sensor/connector. I can approach a hardware technician if the fix demands it.


    * After installing 2nd drive (SSD) on 2011 27'' iMac,
    * CPU and ODD fans are running at full speed, HDD fan at normal.
    * Degraded gaming performance at 6-7fps.
    * Failure in Apple Hardware Test with code TA0P (ambient temperature sensor).

  2. maflynn Moderator


    Staff Member

    May 3, 2009
    Did you try pulling the second drive and getting the computer back to the state prior to the upgrade - is the issue still present then?
  3. Gurpartap Singh thread starter macrumors newbie

    Jun 9, 2010
    I tried that. It didn't help. Perhaps, something went wrong during the initial assembling/disassembling.
  4. Wierzba macrumors newbie

    Apr 13, 2014
    I have similar problem.
    Did you resolve yours?

    Do you know which cable is a signal for LCD temp sensor?
  5. MiBi macrumors newbie

    Sep 22, 2014
    caused by owc temp sensor

    Hi , I have same issue , 27 imac mid 2011 , no problems with fans before upgrade , after installation OWC sensor and SSD - no ambient sensor present , not reversable - if I return fabric HDD and cable , ODD and GPU fan runs at max.

    OWC cable kills something on logicboard , only exchange of logicboard helps. Could you confirm, witch brand of temp sensor for upgrade did you use ?
  6. chihaoly macrumors newbie

    Aug 13, 2015
    My iMac 27" 2011 have a exactly the same problems, I took it to apple just yesterday and after they checking it and tell me that the cable sensor call Ambient not working or missing, so I have to leave my mac there for replace the new sensor cable, that will cost me $53 AUD, but i still waiting the call from them if any other issues, i will let you guy know later... (sorry about my english)
  7. Gurpartap Singh thread starter macrumors newbie

    Jun 9, 2010
    Can you ask them which sensor cable/part was changed to fix the fan problem? A model number or a photo of the part changed would be very helpful.
  8. lakriz macrumors newbie

    Sep 12, 2013
  9. MsFocused, Mar 16, 2017
    Last edited: Mar 16, 2017

    MsFocused macrumors newbie


    Mar 16, 2017
    Just as an FYI - I just did a HDD swap to a Hybrid drive and am having the same problem with roaring fans and a error message that it's a dead Ambient temp sensor that was working before the upgrade. I checked every connection, installed the thermal cable from OWC to the new drive, and still have a beautiful 27" mid-2011 i7, 3.4 Ghz iMac with a new 2T hybrid HDD, 24 Gb memory and roaring fans. (I also own a mid-2011 13" MacBook Pro, a 2009 Mac Pro with a 30" Apple Cinema Display and a 23" Apple Cinema Display but this iMac is an awesome machine and since I am a photographer with huge digital archives, I use it for my main edit station).

    If you note the location of the sensor, it's right about where the LCD screen would make contact with the Logic Board when pulling it forward to remove it from the aluminum case. I suspect that a lot of folks who are making these upgrades are accidentally hitting that sensor when removing the screen or when putting it back in. It's not hard to hit that sensor, and I feel that there should be a warning about this issue in the install video that OWC published to assist customers who want to do a DIY. Mind you, I am not certain that I actually hit the sensor, but it sure seems likely given the number of times I pulled that screen forward while trying to problem-solve the issue of the fans.

    I've done everything that folks here have tried: Reset PRAM, SMC, etc to no avail. I also looked at the Ambient Temp Sensor and pulled it out and stuck it back in without any luck. This sensor wasn't touched during the upgrade, so I just did it to see if it somehow got loose during the procedure.

    This really tics me off, as I'd not have done the upgrade had I known there was a chance of damaging the logic board in this manner. I only replaced the main HDD and added the thermal sensor that OWC provided, so it wasn't like the addition of two drives that requires removing the Logic Board.

    I saw a post somewhere in my quest to repair this damaged Ambient Temp sensor that contained pics of the same problem, and his remedy was to solder the two small dots back on to the Logic Board near the sensor. It makes sense, because I think they get knocked off when the LCD is tilted forward while removing/replacing it during the upgrade. I saw another post where someone found a software program that allowed him to control the fan settings manually, and it worked without much hassle, as the program is in his startup folder and comes on when he boots his machine.

    If anyone has any suggestions re software that will control the Ambient Temp Sensor, I'd greatly appreciate your sharing that information. I'd solder the board like the other people did, but I don't trust myself with a solder tip near the board, as I have a medical condition that leaves me with decreased feeling in my hands. They did it without removing the board, as the area is easy to access, but still, I'm just going to try to go with a software fix for now. I will get a friend to do it when he visits, as he's far more adept at working on intricate circitry..

    I see these posts are rather old, so I hope that someone sees this and can make a good recommendation about software.

    Here is the post re soldering the Logic Board: https://www.ifixit.com/Answers/View...+sensors+or+fans+after+Dual+Drive+Kit+Upgrade

    Thanks so much!!
  10. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    Guys there has been stacks written on the problem of replacing a hard drive with anything but the precise original drive model, and re-attaching the hard drive heat sensor cable. What you describe is precisely what will happen. OWC (macsales.com) worked on this and overcame it with a Heat Sensor Kit.

    This problem applies to all models from late 2009, and for 27" models to current. In 2012 Apple overcme this for thr 21.5" iMac byusing a slow 5400rpm 2.5" laptop style hard drive. Have a read of the link:-

  11. MsFocused macrumors newbie


    Mar 16, 2017
    If you read my post, you'll see where I note that I attached the OWC HDD Thermal Sensor cable for the drive. It's the Ambient Temp sensor that went out during the process, for some reason -- not the HDD sensor that OWC uses to override the internal drive sensors.

    What I really need is a link to a software program that others have tried and is supported in OS X Sierra AND controls Ambient Temp Sensor. Some programs don't control that particular sensor.

  12. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
  13. zone23 macrumors 68000

    May 10, 2012
    This is what I'm currently using on my Mid-2011 iMac it seems to be working fine with Sierra 10.12.4. I installed a SSD drive. I might by the temp senor one of these days.

  14. cdazzo macrumors newbie

    Apr 6, 2017
    --- Post Merged, Apr 6, 2017 ---
    Did you ever get the fans from spinning at full blast to stop?
    I changed the video card in my client's iMac 2011 and now the fans are out of control. Didn't touch the hard drive and reset the SMC and PRAM. Please let me know.


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13 February 25, 2014