So I got myself an adapter and an articulating monitor arm for my late 2013 27" iMac the other day, and with the help of an app allows me to rotate my iMac 90º and use it in portrait mode. The screen looks even bigger vertically! There are lots of situations I would love to use it this way for. However, when I rotate it 90º the fan turns on full blast. Any ideas what this is about? Other than being noisy is there a danger of burning out my fan or wrecking something by running it in portrait mode?
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2013 27" iMac full fan when rotated 90º
- Thread starter DallasL
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The iMac is very specifically designed to be used sitting on the stand in landscape mode. The air flow internally is set up to flow down and out the vents in the bottom of the iMac. By turning the device on its side, you're changing the dynamics of the way the air flows, so the iMac gets hot and the fans come on. You're likely not going to get around this. That being said, I also have a 27" iMac that I have a 30" Dell UltraSharp attached to in portrait setup. It took a really long time to get used to it, but I like it a lot better than having two Landscape mode screens.
That's my thinking as well, but do you think the fans would ramp up so quickly when the computer is turned sideways? Seems like an odd problem.
OP what is the temperature when you hear the fans ramping up?
Yeah, they can start spinning up almost immediately. They're pretty damn sensitive, especially in the newer iMacs (due to the relatively tiny internal space). The MacBook Air is the same way... go to a page with a Flash object/video on it and the fan will almost always instantly crank up.
I'm not sure how to gat a temperature reading 
any suggestions on what app to use for that? I have been googling but not coming up with anything.
Thanks MacGizmo, I think that answers my question. It is pretty crazy how fast the fans kick in, its almost instant! And they turn off almost instantly when returned to horizontal/landscape. Almost make you think there is a accelerometer in there somewhere!
any suggestions on what app to use for that? I have been googling but not coming up with anything.Thanks MacGizmo, I think that answers my question. It is pretty crazy how fast the fans kick in, its almost instant! And they turn off almost instantly when returned to horizontal/landscape. Almost make you think there is a accelerometer in there somewhere!
The late 2012 and newer iMacs do not rely on airflow for cooling. The CPU and GPU heatsinks are connected by heatpipes to a finned radiator that sits directly behind the slots located on the rear above the memory access door. The blower fan pushes the radiator heat out through the slots. This cooling method is much more efficient than the convection based cooling of the previous iMac models. In those, the CPU and GPU coolers heated the interior air which rose and exited via the slot at the top rear. Air entered by the bottom slots.
The fact that your fan speeds up almost instantly points to an electrical, or a mechanical contact issue. If a sensor reading is compromised, the fan will normally speed up. There's a fair bit of weight in the cooling assembly, so something could be moving slightly on rotation. Does it happen with both right and left rotation? The normal portrait rotation is to the right.
The fact that your fan speeds up almost instantly points to an electrical, or a mechanical contact issue. If a sensor reading is compromised, the fan will normally speed up. There's a fair bit of weight in the cooling assembly, so something could be moving slightly on rotation. Does it happen with both right and left rotation? The normal portrait rotation is to the right.