Intel iMac late 2006 lines on screen ONLY after heating up?

Discussion in 'iMac' started by torontonian, Jul 27, 2012.

  1. torontonian, Jul 27, 2012
    Last edited: Jul 27, 2012

    torontonian macrumors newbie

    Jul 27, 2012
    Hi everybody,
    I have been looking into this issue I am having with my iMac. I do see it's a very common problem and Apple is not acknoweledging it. I have googled for several days and have not come across one that has the exact problem as mine.

    So I get those glitchy horizontal lines across the screen. I have smcfancontrol installed to monitor the temperature and fan speeds and occasionally increase them (but not often.) The computer is fine, no lines or glitches until the system temperature goes over 40 - 42 C (104 - 107.6 F). Even when the fans are up it's still heated. No one has ever reported they get lines only after the system heats up. What could this problem be?

    Oh and also, the computer is absolutely fine in safemode (safeboot). I've just noticed that there will be no video which I read is normal because of the limitations safemode causes.

    So is my iMac still salvageable? I heard there might not be permenant damage done to the GPU yet. How would I go about managing and fixing this issue?

    Any help is much appreciated.

    PS - I know that it's time to upgrade, however I love this iMac and I do not want to see it go. It was my first and I'm extremely satisfied with it. I use it for reading, surfing, checking emails and occasional youtube. Most of the time I'm on the go with my laptop or iPad.

    Thanks again!
  2. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    Crank your fans up in SMC, and try blowing compressed air into the bottom of your imac (intake vents), and in the rear (vent directly behind the pedestal in the back) - there might be dust loaded up on the heat exchanger.

    iFixit has a bunch of DIY guides."_EMC_2111
  3. torontonian thread starter macrumors newbie

    Jul 27, 2012
    Thanks for the reply TDI Guy. I will consider doing that. However, I do not have an air compressor. Would I need to open up the iMac and vacuum it?

    Would a regular house vacuum work? Or where would I be able to purchase an air compressor safe enough to clean up the dust?

    Thanks again
  4. AndyCarolan macrumors member

    Jun 25, 2012
    Just buy a can of compressed air from Amazon or local elec store, they're not expensive :)
  5. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    A vacuum will not do as good a job unless you open the unit up, and directly attack the fans and heat exchanger. Even then, I don't favor it, as most house-vacuums generate a LOT of static - which does not serve computers well.

    The "canned air" will work just fine, just crank your fan speeds up to max before hand, so you eject dust from your computer - before it can settle on another surface inside.

    Really try to align the straw / nozzle with the fan locations, and exhaust vents - use the pictures on iFixit to get an idea where you need to aim the air.

    It's the easiest thing that may help, next step would be actually opening your iMac up, and that thing can be a pain to work on, trust me on that. ;)
  6. torontonian, Jul 27, 2012
    Last edited: Jul 27, 2012

    torontonian thread starter macrumors newbie

    Jul 27, 2012
    Thanks a lot for the informative answers. I will definetely do that!

    Sorry to be a noob, but how will the compressed air cans work when the unit is not opened? :eek:

    Could it also be 1 or more fans may not be working? My husband is more educated on opening up electronics. Maybe he would be able to consider as I noticed there are black dust particles on the vent.
  7. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    The velocity of air dragged into the machine is very slow - and not much faster through the fans / exchangers. This allows them to be quiet running - but also allows dust / debris to accumulate. Especially so if you have forced hot air heating, pets, children, smokers or frequent cooking that results in grease / smoke.

    The air going through the iMac is pretty slow under normal operation, whereas compressed / canned air gives you a burst of air that moves MUCH faster, and carries a lot more energy - which stands a far better chance of breaking debris loose.

    The advice against opening your iMac, is just in how cumbersome it is to open, with thin flex cables, torx screws, tape everywhere, and the camera / microphone on the front cover can be broken easily. I'm NOT trying to scare anyone off - but that particular iMac in my view, is much more difficult to open than your average PC. So whenever possible, I try to avoid cracking it open unless it truly needs it. A bad GPU obviously justifies this - not sure cleaning of dust itself does. However if you do open it - the most effective way to remove the dust without damage is using an antistatic brush, or even a cheap paint brush with the bristles rubbed with a dryer sheet. Followed by the compressed air.

    If you use the canned air - get bottles with the straw - it will focus the air, and allows you to get just inside the vents.

    If the fans aren't working - the computer should throw an alert / alarm. To be sure, you can get iStat Nano or SMC Fan Control - and that program will show you the speeds of your 3 fans. If one of them is showing "0" - then that's it. But again, I'm nearly positive the system will throw an alarm / shut down if the cooling fails.
  8. torontonian thread starter macrumors newbie

    Jul 27, 2012
    Thanks so much for your help. :)

    My husband went out and bought a datavac electric duster. We're hoping that will do the trick. What about after the dust is blown, wouldnt the dust still be stuck inside though?
  9. Big-TDI-Guy, Jul 27, 2012
    Last edited: Jul 27, 2012

    Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    That's why you use SMC Fan Control - and crank them up to maximum while you blow the dust out. They normally don't run that high, but running @ maximum alone isn't enough to break the dust free, but it IS enough to eject it from the system once the air burst does its thing.

    Thereafter, you just set your fan speeds to normal - however, I'd advise increasing them minimum speed to keep things cooler - because if it is heat related, and you are seeing artifacts from the GPU - it's likely to continue unless you keep the temps down. (or the erratic behavior / artifacting will become worse over time)

    SMC Fan Control is free, as is iStat Nano. SMC Fan Control allows you to monitor fan speeds and adjust them manually, iStat just lets you monitor temps / speeds, ect...

    Edit: Just to reiterate, you really should get SMC Fan Control - I'm not plugging them, but I have the same iMac as you - and that system was known for developing heat-related issues with the GPU - causing artifacts / crashing of the display. If that is your issue, it will get worse the longer it runs "hot". I've been running my iMac with higher fan speeds, and frequently keep it cleaned out - so I have yet to develop this issue. However I've had this problem on other systems and game consoles - usually once it starts, it'll always be there if it gets too hot, and it will get worse over time. So if this problem happens even after cleaning it out and running the fans higher - you will have to open it up to replace the heatsink compound or else it'll eventually die. The GPU can be replaced, if need be. But I'd bet that cleaning it up, bumping the fans will likely be enough.

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