6 Replies Latest reply: May 17, 2012 11:35 AM by tom manley
tom manley Level 1 (0 points)

My Mac Pro 2008 version has been experiencing intermittent problems for 6 months now and Apple have not yet been able to get to the bottom of this issue.

Initially the machine was not starting up properly ( it would not power up at all - light would come on for a few secs then click off ) and after trying SMC resets and PRAM resets, memory stick checks etc.. i took it into the store.


I was told that the problem may be power supply unit or logic board related... but that on further inspection the problem did not replicate and machine was working ok... So i carried on with machine for a few months with no problem...


Then the same issue started happening and it would fail to complete power up... On taking it back into the store a new power supply unit was ordered but then not fitted due to being told that machine appeared to be working ok...


And now  a few months later it has started to cause problems with start up - and sometimes takes 6 or 7 attempts before a succesful start up occurs...


I was advised to try a hardware test and get a error code 4MOT/1/40000002:EXHAUST-0 which i have no idea what it means....


On installing a system checker 'istat widget' it seems to say that my Exhaust Fan has rpm of 0 - i'm not sure if the app simply cannot detect the fan or if this fan should have a diferent reading...


I am now no further forward in getting this sorted but have booked another appointment with apple store..and want to give them as much info as possible

I think they should have already done a hardware test and be able to pinpoint whether this is a logic board / power supply or exhaust fan issue... I am not sure if this may be related to reason that the machine also shuts down when put into sleep mode ...


Apart from that machine works fine!! Any help appreciated.

Mac Pro, Mac OS X (10.5.8)
  • Topher Kessler Level 6 (9,865 points)

    The exhaust fan on your computer is either not spinning or the sensor is faulty and is not sending feedback to the system management controller. This could indicate a power supply issue if the fan is not being properly powered, especially since at times it would not power on properly.


    My overall guess here would be that it's a power supply issue, and you would benefit from having it replaced with a new one.

  • bbolander Level 1 (0 points)

    my 2-1/2 yr old macpro has had problems not starting at all when pushing the start button.  for a while the smc start worked, then nothing did.  took it into the genius today, started right up and tested perfect using their power cord, wouldn't start with my power cord.  brought one of their power cords home as a temp and started up fine so far.  so if this fix remains to work, might just be the power cord.

  • tom manley Level 1 (0 points)

    Thanks for comments ... It certainly looks like the Exhaust fan is not spinning - or like you say the sensor does not detect it... Is there somewhere within Mac OS which says if the fan is working properly? -  and if it is not working is replacing the power supply unit likely to get the fan working - i'm thinking maybe it is just the fan or the fan and power supply unit that i need... It is booked in for appointment today - which hopefuully will get to the bottom of it - took about an hour to get started today - not good!!

  • Grant Bennet-Alder Level 9 (56,679 points)

    tom manley-


    You have taken the next step i was going to recommend. The guys at the genius bar often have spare fans they can substitute and spare Macs they can use to power your fan to do the troubleshooting. This can determine whether the fan itself is a problem.


    Conventional Wisdom for Power problems has you removing everything that could potentially be dragging down the power, and building back up until the last component added causes a problem. (It may be that your fan was failing in a way that caused power problems.) Do not be alarmed if they want to massively dis-assemble your Mac.


    I think they try not to do large-scale dis-assembly at the counter, but taking it in the back to do it takes them away from the counter where they may be multi-tasking -- helping two customers at once.


    Figuring out whether your Power Supply is working properly is a much more subtle problem. But there are some LEDs inside the cabinet that generally light up at power-on, then extinguish when no fault is found.

  • bbolander Level 1 (0 points)

    well, it worked for a few times but is back to not starting.  for a while if i would wiggle the power cord at the tower it would start right up on the 2nd try, now doesn't want to start again.  back to the genius next week.

  • tom manley Level 1 (0 points)

    The power supply has now been replaced by the mac store and all seems to be working well including fan that was apparently not connected properly. However with a new power supply all seems to be working ok... The machine also sleeps and starts up properly which had been experiencing intermittant problems.


    All seems ok now !