Northbridge temperature sensors going crazy!
I'm on a Unibody A1342 MacBook Core 2 Duo 2.4 13" (Mid-2010) that I've modified with extra RAM, a new HDD, and a new battery. It's been running on El Capitan for about a year, with no hardware changes or OSX changes.
The fan started acting up as of late. I tried all the usual solutions: killing processes in Activity Monitor that could be overloading the CPU, reseting PRAM and SMC, even taking the back off and cleaning with compressed air and lubricating the fan axle, but to no avail. I upgraded to Sierra and the problem persisted. I use DiskDrill to monitor temperature and the CPU never went above 35C so I didn't think it was a temperature problem.
I downloaded TG Pro to more accurately check out my temperatures to make sure, and was surprised to find that almost all the Northbridge sensors were reporting incredibly high temperatures, or cutting out sporadically and reporting nothing at all. Everything was normal except Northbridge TN0S, TN1E, TN1F, TN1S, and the second core sensor. These all would spike over 90C, causing my fan to go crazy. This must be what has been making my fan run so loudly at 6200RPM. After continuing to monitor their temperatures, I saw that they would sometimes all cut out at the same time, and display "N/A" in place of a temperature.
Screenshots of TG Pro results:
So, I went ahead and cleaned out and reapplied new Arctic Silver 5 thermal paste on the heatsink, hoping that the problem was due to a bad connection. This did not work however, and there has been no change in spike temperatures.
Are my Northbridge sensors broken? It seems strange that they would be reading such high temperatures all of a sudden for no apparent reason, when the CPU is not overloaded and there have been no significant hardware changes. If this is the case, what is the necessary solution?