iMac CPU fan stuck at full speed

[ruutiveijari]

I bought a used iMac today (Late 2006: 24", 2.16GHz, 7600GT) and for some reason the CPU fan keeps running at 3200RPM. I've googled for a couple of hours now for solutions and have tried resetting the SMC, resetting the PRAM, keeping it disconnected from everything (power, keyboard, mouse) for 30 mins and none of these have fixed my problem. According to iStat all of the temps are low and the two other fans (HD and optical) run at their lowest speed.

So I'm at a loss and would REALLY appreciate help.

EDIT: Also, is it normal for the system profiler to show 4 GB of memory installed when this model is supposed to support only 3 GB? I removed the other memory and tried booting after that but it didn't fix my problem.

 

[Jeremy1026]

Run "Apple Hardware Test" (Google it to find out how, as I'm not sure how to do it on your generation of iMac). It will test the fans and report back if you have any issues, and sometimes can even fix the issues.

 

[ruutiveijari]

Run "Apple Hardware Test" (Google it to find out how, as I'm not sure how to do it on your generation of iMac). It will test the fans and report back if you have any issues, and sometimes can even fix the issues.

Thanks for the tip! I ran the test and it gave me an error: 4SNS/1/4000000:TGOH

Apparently SNS is short for sensor. As the machine was fine and working yesterday, I'm guessing a sensor got loose during delivery. Is there a guide online on how to open a machine like this? I've opened Mini's and iMac G5's before but never on a Intel iMac.