Chosen Solution
I recently reinstalled a video card to my 2011 imac 27” After re-assembly, the ODD fan is running non stop 3500 rpm. After an Apple Hardware Test I received this error: 4SNS/1/C0000008:TS0P–124. Also included a screen grab of the Temps Ive looked into all the sensors attached to the logic board and everything looks ok, although the Skin Temp sensor might be damaged, Is this sensor controlling the ODD fan?
@jonnyvtg L5500 and L5501 are inductors for the ambient temperature sensor. L5510 and L5511 are for the ODD temp sensor
Yes, a failed right skin sensor can get the fans running at full speed. Remember that the fans are set to high by the hardware at the iMac’s startup. They are set to slower speeds several times a second by software, based on the various temperature sensor readings. So, if a sensor fails the fans go to high automatically.
Lets see the damage you think you may have to the Skin Temp sensor. also, looking at your fan speed, it seems a bit low. I would expect it to run faster
A common issue in this series is people tend to damage the sensor inductors L5500 & L5501 when lifting the cable connections located here:
