PSU Overheating? Loud Fans - replacement PSU?
I can see that this machine and fans have been discussed many times on this forum I've looked through the Questions here on iFixit and elsewhere but can't find a definitive answer to my problem.
I have a 24-inch 2.8GHz C2D iMac Early 2008 Model.
This machine has been wonderful since I've had it and I love it. About two months ago I noticed the Fans starting to get quicker and louder. Nothing in the iMac had changed prior to this occurring.
I have ran AHT on loop and no problems found.
I have dismantled the iMac to clean out all the fans and air vents.
Its not always the same fan that is going full pelt and sometimes its more than one.
Temperatures are as follows (give or take a few 'C)
HD - 51c
CPU - 45c
CPU Heatsink - 47c
Airport Card - 42c
Ambient - 30c
GPU - 60c
GPU Diode - 62c
GPU Heatsink - 58c
PSU - 90c
From what I have read with the exception of the PSU the above temperatures seem normal. I'm guessing that as the PSU doesn't have its own Fan that the other fans are kicking in to prevent damage.
If I reach around the back of the iMac from the front the middle/top/left of the case is extremely hot and can only be touched for a few moments before you have to remove your hand.
Occasionally after long periods of work the iMac switches off and I have to restart.
I have reset SMC, PMU done AHT etc...
Can anyone advise or share their experience if they think that a replacement PSU would solve the problem or is it possible that this is just masking a deeper problem with my iMac.
Sorry for the delay in responding. I've been away doing other stuff.
No i've not resolved the problem yet - i've been living with it and have suffered the odd cut out due to over heating.
Just to recap - the replacement power supply didn't resolve the issue.
I suspect its the graphics card or logic board so will probably live with it for a bit and then sell it for spares/repairs.
If anyone has any input will be much appreciated.
Sorry for the delay in updating this post. I have only just been able to get my hands back on the iMac for further testing.
I replaced the PSU but unfortunately it has not resolved the issue and after about 10 mins of use the fans were cranked right up again.
I noted the temperatures in my original post of the components and here they are again now as I am using the iMac.
all in Celsius
CPU A Heatsink 44
CPU A Proximity 45
CPU A Temp Diode 42
CPU Core 1 45
CPU CORE 2 41
Display Screen Prox 51
Graphics Processor Chip 1 56
Graphics Processor Heatsink 1 56
Graphics Processor Tem D 58
Hard Drive Bay 1 50
Main Logic Board 47
Optical Drive 41
Power Supply Position 1 84
Wireless Module 55
From what I have read all the temperatures seem to be normal and the PSU temp is the only one that is causing me some concern. I'm not sure whether it is perhaps a faulty sensor or sensor cable and whether anyone has experience on this?
I am 100% confident that it is not software. I have another identical iMac here that I have loaned to my customer and 'cloned' the hard disks and the problem has stayed with the iMac rather than the software. At the moment I only have Text Edit, Safari and Activity monitor open and the system is 93% Idle.
I left the iMac running AHT on loop over night and it through up an error message 4SNS/1/40000000:Tp0P-93.050
Apple Service Source response to this error code
Suspected part - Power supply sensor pin/power supply,
Suggested Action - Verify that the single pin connector on the top edge of the power supply is present and securely plugged in. If connector is damaged replace the DC Power Supply cable. Notes - If this sensor signal wire is disconnected or faulty the CPU fan will run at full speed.
I have tried a replacement Power Supply that did not solve the problem, the sensor pin on both Power Supplies looked fine. The pin connector is securely plugged in.
The problem is that the Fans run at full speed all the time only after a few hours of use which is probably why the AHT got this message only after being on test for 2.5 hours after it had chance for the Fans to get up to speed.
I may try getting a replacement DC Power Supply Cable but I'm not convinced and its a !@#$ of a job!
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