Fan issue (gpu related?)

Question

Hi,
I bought an 21,5" iMac i3 3,2ghz, 4gb ram, 1TB hdd, ati radeon hd5670 in December 2010 and i love it (my first mac).
I haven't had any problems at all until a couple of weeks ago when i was playing world of warcraft and the FPS went from 60 to 10 and the fans started to run a bit high. After 30-40 sec the fans and the game went back to normal again for about 3 min then it was full of lag and the fans got going again.
A week after that (i went back playing on my pc for a while because of this) i started WoW again and played for 30 min when the game went unplayable again. But this time the cpu-fan went up to 4000rpm and the optical drive fan to 3600rpm and it never stopped until i shut the computer down.
I searched the internet for similar problems but couldn't find anything related to what i have so i tried sms-reset but with no luck and the apple hardware test said nothing.
3 days ago I decided to give smcfancontrol a try and gave the fans a small boost: Cpu Fan from 1200 up to 2100rpm, the Optical Drive Fan from 999 up to 1850rpm and the Hdd Fan from 1100 up to 1550rpm and this actually worked very well. The temps where low and the gameplay experience where perfect until this morning.
I woke up and turned on the iMac and opened safari when the fans started to blow like crazy and only a shut down could fix it. I run the hardware test and got this message: 4SMC/1/40000000:SMC
I deleted smcfancontrol just in case and tried smc-reset and did the hardware test again and got the same message.
I decided to call Apple for support and they told me to reset the computer to factory-default and i did. The fans blowed like crazy until i got to like 50% of the new install and then they stopped and everything seemed normal after the installation was complete. I ran hardware test and the message was gone. I waited a couple of hours and then i installed WoW again and after 5-10 minutes of gameplay the fans started to go wild again. Another hardware check and the message is there again but after the next re-start its gone.
This is the average temperatures i experience when gaming:
CPU: 58c
HDD: 53c
GPU Diode: 82c
GPU Heatsink: 76c
Powersupply: 80c
Temps seems normal to me.
This is driving me crazy and I can't think of other than this is a hardware problem when the computer have worked just fine until a couple of weeks ago.
Is there someone who have experienced anything like this that can give me a helping hand?

Answer 1

I took my imac to an apple repair-tech Feb 16 and got it back after 1 week and they told me they couldn't find any problems. They even wanted me to pay for the work they did because they said it was related to the software. I even left a BIG note with the computer with the error codes and an explanation of what's going on but they just ignored it and only did Apple hardware test which did not show anything at that moment.
The imac worked fine without problems for 15 days after that and then i have had the same problem every single f***g day, even now when i'm typing this message the fans are nuts.
I can reset it sometimes by restarting, shut down, smc-reset and some apple hardware tests (not kidding, all of these steps several times). It takes about an hour with these steps every day and then it works fine until it goes to sleep or i shut it down then i have to repeat this steps again for an hour to get it back to normal.
I have not installed anything new on the imac since i got it back and i have manually wrote down time, date and error codes on paper every time this happens. I now have 10 pages I even have some screenshots of istat showing temps and fan speeds.
I am going to contact another repair-tech later and show these papers i have written and the screenshots and see i they believe me then. I really hope they do because i'm so sick and tired of this imac now. And it feels really sad that i'm not able to use it as i want to because of this.
As related to my problem i found the apple technician guide for my imac and this is what it says:
"...if a sensor error is detected, AHT will report an error code containing the affected sensor name (ex: “4SNS/1/40000000 TC0H” error codereports to sensor TC0H)."
My sensor is the TS2P and for that the guide says: "Excessive upper internal enclosure temperature, or Bluetooth/camera/sensor damaged/disconnected from top of logic board" and for the Suggested action: "Verify that the Bluetooth/camera/sensor cable is securely connected to the top of the logic board. Replace the cable if damaged"
This means that in my case, its a sensor thats probably loose or broken because both the camera and the bluetooth works fine.
I think it is a shame that I as a consumer is forced to dig out this info on my own from their own Technician Guide.
I let you know what happens when i have contacted the tech.