Early-2009 iMac 24': GPU temp. is 129ºC; normal or abnormal?

[Nguyen Duc Hieu]

My iMac (purchased from a junk shop) shows quite high temperature of GPU.
Youtube videos are stuttering.
Is there anything should I do? Or tell the service shop to do?
CPU temp and other temps seem normal to me.
I installed FanControl and set CPU fan speed to 3000rpm, but it was not effective on GPU temp. It's always 129ºC

 

[DeltaMac]

That's -- too hot!
Open up the case, remove the logic board, then remove the CPU card from that logic board.
Make sure that the cooling passages are all clean and clear -- CPU fan, too!
Re-apply the GPU heat sink compound.
(I suggest that you also re-apply CPU heat sink compound, while you have everything out.)
Reassemble, making sure the GPU temp sensor is plugged in properly.
That's just about everything you can do... Hopefully, the GPU has not been damaged by the heat.

 

[Juicy Box]

Thermal paste dries up overtime becoming less effective. It most likely needs to be reapplied.

 

[Nguyen Duc Hieu]

I was running the iMac for almost 10 hours before detecting the abnormal temp read from HWSensore.
Another possibility: HWSensor readings were weird...
I've also seen a Youtube video which showed a physical defect in the GPU heatsink (tiny leak hole on the copper tube that exhausted all the coolants)
Anyway, I'll try opening the case and read the temp by another thermometer just to be sure, after a thorough cleaning and re-applying of thermal paste.
Thank you.

 

[r6mile]

129 just means there is no sensor, or can't get a reading! If it's concerning it would flash up in orange or red. You'll see that it will just stay at 129, not go to 128 or anything. It's just the HWMonitor way of showing no reading.

 

[DeltaMac]

129 just means there is no sensor, or can't get a reading! If it's concerning it would flash up in orange or red. You'll see that it will just stay at 129, not go to 128 or anything. It's just the HWMonitor way of showing no reading.

That does sound like a good way to go for a check. Your model iMac video card has an actual 2-wire connection, but you have to take the logic board out to even check for that connection.

 

[Nguyen Duc Hieu]

Thank you very much.
Now I feel a lot of relief.
I will try to open the case to peek inside and try to re-attach the GPU sensor if possible.
If it's dusty, I'll bring it to the shop. The shop here charges me only 10$ for cleaning and re-applying thermal paste.