10 Replies Latest reply: May 9, 2007 2:48 AM by Wolpy
D. E. Campbell Level 1 (0 points)
I recently bought a used Mac Mini G4, 1.25 gHz. It has been working great. It does often overheat when doing anything demandingly graphical or when burning a CD, however. It's fan becomes exceedingly loud and the computer goes to sleep.

This is mostly an annoyance; no damage has been done to the Mac Mini, but I am wondering why it is happening. I am currently a college student living in an air-conditioned dorm. The room is not hot, and the Mini has plenty of room to properly ventilate.

Could the heat sink be loose or slightly off, or is this a problem with a temperature sensor? Any ideas would be greatly appreciated.

Thank you!

Mac Mini G4 (1.25 gHz), Mac OS X (10.4.9)
  • AndyO Level 6 (17,050 points)
    Welcome to Apple Discussions!

    It has to be said that while it's not uncommon to provoke a G4 mini into very loud fan activity, even if only for brief periods, it's not at all common to have one that overheats to the point of reaching it's protective shutdown - and certainly not in a temperature controlled environment unless the system is being pushed really hard for prolonged periods.

    It is likely that the heat sink is loose, that the thermal pad at the base of the unit that helps drain heat from the CPU to the baseplate is degraded, or that the air ducts are partially blocked. A careful application of a compressed air spray, or lens cleaning air blower would help ensure it isn't the latter, leaving an internal examination and possible repair as the only other probables.
  • Boece Level 5 (6,245 points)
    In a recent thread about an overheating, second-hand Mini, the cause was apparently that the bracket holding the heatsink to the CPU was not attached at all corners.

    There is also a fan sensor wire that sometimes does not get re-attached properly after a mini has been disassembled. But this usually causes the fan to run all the time.

    Is there evidence that your Mini has been previously opened?

    You say that the mini goes to sleep? Or does it shut off? If it is protecting itself from overheating, I would expect it to shut off, not go to sleep.
  • D. E. Campbell Level 1 (0 points)
    The mini goes into a shutdown mode (the light pulsates, etc.) It can be woken up fine by moving the mouse or hitting a key.

    Also, the case seems to be in perfect condition. I can't see any evidence of it being cracked before.
  • AndyO Level 6 (17,050 points)
    The sensor wire for the fan is something that is problematic on the Intel minis, but not so far on the PPC models that I know of, but it's still possible that either through prior work or possibly faulty manufacture, that the CPU heat sink has loosened. It is certainly possible that the thermal pad has degraded since it's been noted in a small proportion of PPC minis.

    When the system goes into protective shutdown, is the base of the unit warm-to-hot to the touch, or cool? If cool then the thermal pad is suspect and that's not an easy fix, though the pad itself is a service part Apple's service providers can obtain. If the base is at least rather warm to the touch at that point, then likely it's the heat sink.

    If you feel confident, you might try opening the case to check there are no major obstructions to the airflow and perhaps running it like that for a time to see if the same operating conditions still cause it to shut down. With the top off, it should run a little cooler, but a detached heat sink would mean overheating is inevitable under load.
  • Bozz_2006 Level 3 (505 points)
    just because it doesn't appear to have been opened doesn't mean that it hasn't been opened. I opened my mini to upgrade the RAM. I was a first-timer and my mini is still in perfect shape. and if i can open it without breaking anything, anybody can.
  • francism Level 1 (0 points)
    About 8 months ago, my G4 mini (bought new, and not moved about) started to shut down at random, about once a week, both when working and when sleeping; the only cure seemed to be to unplug the power adapter and leave everyting for a good while. This made me wonder if the problem was in the power adapter or one involving overheating in the mini itself. After about 6 weeks of this, it seemed to cure itself, and I thought little more of it. (btw, the label on the power adapter said it was Part Number 611-0398, made in Thailand, but when I checked this on-line, I get a different number for the 85W unit.)

    Last week, when printing, I sent a document to the "wrong" printer, and aborted the print. Within a minute, the whole system shut itself down (with a click-sound from the LCD monitor I think.) Since then, it has been doing it more and more frequently. And the run-time is getting shorter and shorter. It's now unusable.

    Remembering what I had read here during the previous problems, I reset the PRAM, used the vacuum cleaner to clear out all the slots on the back and on the underside of the mini, and reset the PMU. I have been unable to run disc utility or the hardware test as I can't get the mini to run for more than about 30 seconds, so I can't yet get any further info about what's going on.

    Thinking that it may be an over-heating problem, I'm considering putting the mini and the power adapter into the fridge overnight to get them near the lower end of the temperature operating range, and thereby extend the running time (but I won't try this yet without some assurance regarding problems that may arise from condensation into the mini when I take it out into the room).

    Any ideas, please.

  • AndyO Level 6 (17,050 points)
    Thinking that it may be an over-heating problem, I'm
    considering putting the mini and the power adapter
    into the fridge overnight to get them near the lower
    end of the temperature operating range, and thereby
    extend the running time (but I won't try this yet
    without some assurance regarding problems that may
    arise from condensation into the mini when I take it

    This is really NOT a good idea. The system isn't designed to be refrigerated and while temperatures are not extreme in the average fridge, the chilling effect followed by the swift heating to normal (or above normal) temperatures would risk causing significant heat stressing problems, including the breakdown of thermal pad bonding, creating open (or intermittent) connections or causing tracks to lift. Additionally, as you realise, there is a danger of condensation forming which could cause a variety of failure conditions, some of which could render the system anything from unstable to non-operative.

    This would be a situation where an apple approved service provider may be a rather better option to pursue!
  • Wolpy Level 1 (5 points)
    Hi, my MacMini Intel (Early 2006) every few weeks switches off overheated (at about 80 degrees Celsius processor temperature), because obviously the fan didn't run. The Hardware test program recently showed the error codes
    4MOT/1/40000002: Center_Upper-Front
    and in the "About this Mac"-data I find this similar code
    4SNS/1/40000002: Center_Upper-Front
    My German GRAVIS Store for Apple products was not able to recognise the real cause for this repeatedly occurring temporary failure and argued, that even the contacted German Apple Support actually doesn't know this error codes!!
    What shall we think about Apple's quality assurance and qualified product support? Is it restricted to the Chinese production plants or Apple development departments?
    Does anybody know, where HW error codes are documented?

    Mac-Mini Intel Mac OS X (10.4.9) Mac user for 15 years

    Mac-Mini Intel   Mac OS X (10.4.9)   Mac user for 15 years
  • triciaGilsland Level 1 (0 points)
    Could be a power supply problem My mini, had a faulty power supply from new, the power cut off when I moved it. I didn't realise it was delivering incorrect voltages until the hard disc failed; the first component likely to go with variable voltages. Mini was returned with a new power supply, hard-drive and a continuously working fan. Previously the fan had never once turned on yet machine had run hot at times. I was told that the faulty power supply may not have been able to deliver enough power to drive the fan? The new fault was resolved when the hard drive sensor cable was reconnected. What else might fail soon given a a faulty power supply and no fan for 10 months?
  • Wolpy Level 1 (5 points)
    Thanks for your contribution. I know from my own experience, that China-manufactured power supplies and other hardware tend to be not of best quality. But in my case obviously the temperature and fan control inside the Mac case fails sporadically, of what cause ever. What I get upset about is, that the Apple technicians were not able to use the error messages from the hardware test program in order to identify the source of that malfunction.