18 month old 27″ iMac is giving a bit of grief at the moment. Switches on when cold and runs for 1/2 hour or so before starting to randomly reset. First thought is overheating and have cleaned the vents and installed mac fan software. That’s not made any improvement and not showing any errors.

Any ideas? (Yes I have a PC too thanks)

Take it back to Apple, two year EU warranty on electrical goods.

If it were a PC, after checking fans / air vents I’d probably replace the thermal paste on the CPU. God knows how accessible that is on a Mac though. Go see a Genius.

non i owner….but

heat issues, thermal contacts between chip and cooler, how long does it take to cool down/wait before it restarts? How old is it?

How old is it?

18 month old 27″ iMac is giving a bit of grief at the moment.

😉

cheers Count c- in comprehension. reasoning stands though however at that young return to apple as they never fail 😉 (it must be a faulty one!)

Get down to an Apple shop and book a Genius appointment. They will sort you out.

Try not to go on a Saturday if you can avoid it, they are usually rammed then

do the usual permissions repair and reset pram (do any software updates before this)
or try onyx and clear all the caches and do the verify/repair from there.

I had a PC that did something similar. On that it was the fan driver circuit. I plugged the main fan into another fan socket and it worked fine. No idea how this applies to an iMac but as above if it is only 18 months old head back to the shop

Also do an SMC reset.

Worth reseating the RAM too, as it’s (usually) a simple job that wouldn’t affect any warranty should you need to take it back. But I’d agree it sounds suspiciously like a cooling issue on the CPU.

thanks all, some work for the weekend

a little update in case someone else with same issues

using the mac fan software I’ve isolated the issue as being an overheating CPU. by running CPU fan at full tilt it has not reset in over 48 hours. now to find whether it is the fan or the CPU at fault….

I refer you to my first post.

(-:

Could be the GPU also (not sure if iMac’s have those) (or if you can access them).

Sounds like a fan bearing has gone, or thermal paste, or dust etc.

Unfortunately it seems taking it back is the best option.