Ask HN: How is my MacBook temp getting misread?

5 points by GWBullshit 353 days ago | 9 comments

Ever since the last MacOS update, my MacBook has been overheating very easily, very often. When this happened in the past, I would simply put it in the freezer for a few minutes and then pull it out and get back to work. Now something strange is happening: The MacBook itself will be ice-cold, but unlike before when it would just resume working wonderfully, now it "sort of" works, but not really. For example synching stops and says "It needs to wait until the temperature drops". I installed an app to see what's going on and it's reading the CPU at 190º+ F and the GPU at 200º+. Why? How could anything inside be that hot when the frame itself is ice cold?

leakycap 353 days ago |

MacBooks are metal. When you put them in the freezer, the likelihood of moisture damage, especially around very hot components, is much higher than if you try this with a plastic electronic device. I wouldn't put metal laptops in the freezer, as damage to small sensors could be your issue. In fact, anything with thermal paste really shouldn't go in the freezer. But too late to undo that, you can stop doing it though.

The way macOS/ firmware handles cooling can be confusing. Have you tried rebooting in single user mode and checked the temps from there? Have you ran the hardware diagnostics from boot?

GWBullshit 352 days ago | |

Appreciate the reply and advice.

Having said that I've had this model for quite a while now and have been doing this since I can remember and never had this issue until the latest macOS update, which from what I've researched seems to be affecting loads of people with all sorts of newer, much fancier processors than what I have.

While I will definitely keep your advice in mind going forward, it seems that this issue sprung up only after this last update, which is strange because I remember reading something about "improved energy management" or some such.

apothegm 353 days ago |

The metal frame of a MacBook is part of the cooling apparatus. If something in the heat conduction chain got messed up (see the earlier comment about freezers and thermal paste), the chips are unable to shed their heat into the frame the way they’re meant to. Keeping the frame cooler than usual, while the chip quickly overheats.

GWBullshit 352 days ago | |

If the frame is ice cold, wouldn't the heat from the processor dissipate faster into any adjacent thing that is much colder?

apothegm 352 days ago | | |

Air is a very poor heat conductor, and among the best insulators. The thermal paste conducts the heat much more quickly. If it’s not touching maximum surface area on the things you want to conduct heat between, and the heat has to dissipate solely through the air that’s touching the processor, that’s much less effective at cooling.

_wire_ 353 days ago |

A fissure in the thermal bonding compound between the chip and the heat spreader, or a loose heatspreader anchor screw causing the spreader to lose fit to the chip. Either can result from a fall or other shock, or a manufacturing defect.

GWBullshit 352 days ago | |

Thank you for you reply, I'll make note of this if I go to a repair shop.

Just not sure how the processor definitely works very smooth, very fast, just like as if I restarted it whenever I take it out of the fridge, but the sensor is somehow reading ~200º.

aurizon 353 days ago |

open up, remove heat sinked parts, clean both faces with isopropyl alcohol. Buy some 'cooler master' paste and reseat. Take care with minimal alcohol and power off - it can catch fire. Most repair shops can do this - ask first

GWBullshit 352 days ago | |

Thank you for the reply and advice – I will probably pursue this if it keeps up, even though it seems to have happened much more dramatically after the last OS update.

Regardless, I'm still unsure how it can read these temperatures since the "put in freezer for a while" method seems to work when it does this and everything gets "un-sluggish" right away and starts working as well as if I restart it, no matter how many things are open.

So it's like the processor "works as if it wasn't overheating", but for some reason the temperature readings for things like synching sometimes don't work because it reads the temp as approaching ~200º, and even external apps read it as such (though I realize they may just be repeating an internal OS error).