The Apple Files

Jason Siebert, aka Sieb (thatsiebguy), who took the photo of the melted insulation featured on our demystified post points out that the shut downs may be caused NOT by an electrical short circuit problem but rather by the high levels of heat that the sensor cables are exposed to. Heat increases the resistance of the electric sensor cable and this results in a decrease in the current through the cable which in turns lead to altering the signal sent by the heat sensor (thermistor). If this signal indicates a high enough temperature, it is possible that the MacBook just shuts itself down to prevent any damage to the processor.

Sieb reports that he did NOT see any physical contact between the two wires (of the sensor cable) when he pulled them apart although the insulation was brittle. He also found that moving the sensor cables away from the heat sink stopped the shut downs:

Moving them away from the heatsink has solved my problem and I have been using my Macbook since without any issues. I’m keeping an eye on it though. I wouldn’t mind coming across a replacement heatsink somewhere online if anyone sells any down the road.

Thanks Sieb!