I see this thread has been going for some time and it is the best one I found on the Internet so far. I purchased a new SSD drive for my late 2009 27" iMac and before I dismantle everything, I would like to be prepared for all operations in advance. This includes replacing the HDD by a SSD but also deal with the Thermal sensor issue.
I find [http://www.ifixit.com/Answers/View/85991/replace+the+hard+drive%2C+how+do+I+connect+Hard+Drive+thermal+sensor#answer108508|Alexandre's] answer to use a 2N3904 transistor simple and interesting and would like to know a little more about it, so please allow me to ask a few questions:
1. Has this solution been tested and validated by anyone?
2. If so, does this setup provide a temperature reading when using a tool such as MacsFanControl or iStat Pro?
3. Does the reported temperature (and variation) make sense?
4. Does this solution allow HDD Fan to behave normally - without any additional software control (ie. not spin at max speed at startup and increase speed reasonably if temperature goes up)?
If this solution has not proven to work, I will most certainly just jump the connector, but will then have a zero reading for that sensor :-(
Thanks in advance