I recently opened the imac to clean out dust as the CPU fan was being loud. I also removed the logic board in order to inspect the CPU fan and clean it. I put it all back together and started it up. It started fine but then about 20 seconds later all the fans were spinning too high. I checked to see that all sensors were plugged in properly and some I had forgot to plug in (never work tired) so I plugged them in. Now upon restarting 20 seconds later only the right ODD fan spins too high.
I downloaded istat to confirm this and indeed the ODD fan is at 3400rpm which is higher than the normal 1k or so.
I did a system check and returned the following error:
4sns/1/C0000008: TGOH—124
Which according to the service manual means the GPU sensor has failed. I inspected the sensor cable from its core in the center of the GPU all the way to the ends as well as ensured it was well plugged into the board which had good solders. All checked out which didn't surprise me since removing the logic board does not require one to unplug the GPU sensor.
Anyway still no luck getting that ODD fan to stop spinning so high. I tried resetting the PRAM and the SMC and still no luck. I also wondered if there was some way to just test the sensor itself so I checked the GPU temp which was between 95-107 fahrenheit (warms up after startup) and then checked it again after disconnecting the GPU temp sensor. Interestingly I got the same GPU temperature of between 95-107 fahrenheit!
It would be terribly sad (not to mention a financial risk) to assume I must replace the GPU just because the little simple sensor went bad. The computer otherwise runs fine.
Any ideas on how to find the exact problem without wasting hundreds on a new GPU and or logic board?
Oh and apple wasted my time when genius bar guy said he would diagnose it even though I opened it and then when picking it up the manager said they could not do anything since I had.
Thanks!
Here are my specs:
Model Name: iMac
Model Identifier: iMac12,2
Processor Name: Intel Core i7
Processor Speed: 3.4 GHz
GPU: AMD Radeon HD 6970M 1024 MB
I downloaded istat to confirm this and indeed the ODD fan is at 3400rpm which is higher than the normal 1k or so.
I did a system check and returned the following error:
4sns/1/C0000008: TGOH—124
Which according to the service manual means the GPU sensor has failed. I inspected the sensor cable from its core in the center of the GPU all the way to the ends as well as ensured it was well plugged into the board which had good solders. All checked out which didn't surprise me since removing the logic board does not require one to unplug the GPU sensor.
Anyway still no luck getting that ODD fan to stop spinning so high. I tried resetting the PRAM and the SMC and still no luck. I also wondered if there was some way to just test the sensor itself so I checked the GPU temp which was between 95-107 fahrenheit (warms up after startup) and then checked it again after disconnecting the GPU temp sensor. Interestingly I got the same GPU temperature of between 95-107 fahrenheit!
It would be terribly sad (not to mention a financial risk) to assume I must replace the GPU just because the little simple sensor went bad. The computer otherwise runs fine.
Any ideas on how to find the exact problem without wasting hundreds on a new GPU and or logic board?
Oh and apple wasted my time when genius bar guy said he would diagnose it even though I opened it and then when picking it up the manager said they could not do anything since I had.
Thanks!
Here are my specs:
Model Name: iMac
Model Identifier: iMac12,2
Processor Name: Intel Core i7
Processor Speed: 3.4 GHz
GPU: AMD Radeon HD 6970M 1024 MB