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My iMac’s (i3 ,WD 500G ) Hard Drive is failure and I replace a new one but I can’t connect thermal sensor to new Hard Drive because the connectors are different. So my Hard Drive Fan will run the full speed after 10 mins when I power on. I google the solution and someone suggest that I can jump the connector to make the sensor short then it will show 0 C degree. It works but I afraid the Hard Drive will overheat when I use for a long time. Do you have any solution to solve this problem? Thank you.

Apple changed to a seven lead temperature sensor and proprietary firmware in their hard drives in late 2009. Their thinking appears to be that no one but Apple or an Authorized Service Provider has the ability to change a hard drive. So you have to go through Apple to get a drive that won’t make the fans run at full speed. To date, I have seen no work around on this site or any other to get around this. Thus you are at the mercy of Apple on pricing. I do expect to see a class action law suit on this soon but who knows when and it doesn’t help you now. I would contact Apple to see if they will help you at all. Please let us know your results.

The best solution, is using a Transistor 2N3904. Just remove the connector (side HD) and solder a 2N3904. Gray wire on E (Transistor) and black wire on BC (transistor). By Alexandre Larangeira

I have used the sensors from earlier iMacs as well as from Macbook Pros. The Macbook Pro aluminum models are the ones I usually use. There are several of them, I usually use the ones that are under each fan. They have 2 leads just like the iMac which I extend to reach the drive. Then i attach the sensor with double-sided tape (same stuff we use to adhere glass on iPads and unibody MacBooks). The sensors from earlier iMacs (if they are the 2 lead type) also work. Some splicing is usually required. I have done it this way since the very first drive replacement I had to do on one of these iMacs. I don’t think that any resistor or jumper is a good idea at all. Temperatures in a computer need to be monitored and the fans adjusted continuously for everything to work at peak efficiency. I don’t want to leave fan control up to my clients to monitor. Nor do I want their iMacs running noisily because their fans have to be run at high speed all the time. I’m perfectly willing to hack and modify things when it makes sense, (my Hackintosh is over- clocked to 4.7GHz, and I install Mt Lion and Mavericks on unsupported Macs all the time) but in this case it doesn’t make sense.

Macbook Pro A1150 right fan ambient temperature sensor. Splice one of these (black to black and color to color) to your old sensor cable and stick it to the hard drive. The hard drive fan will function just as it did with the original drive. People have over-thought this problem. My thinking was: I can’t use the internal sensor so I need an external one. I have all these other mac parts. Maybe the sensor from another Mac will work. Lets try a Macbook Pro sensor. Splice the wires and try it out. Works fine, all temps check out. Simple

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 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

I have an Independent Apple repair business here in Oregon. This issue is really not an issue. Apple was not trying to prevent anyone from replacing hard drives. Apple was trying to save money by using the built in sensor in the HDD instead of adding their own external one. I have used many other temp sensors from other Macs for this. My reasoning is that if I have to alter the cable I may as well make it easier on the next tech by adding an external Apple temp sensor from another Mac. The temp senders Apple uses are surprisingly standardized. I have checked them with an infrared thermometer and they appear to have similar specs.

I know this is an older thread, but here’s something I’ve found. If you’re replacing a WD drive, you need to rotate the temp sensor connector 180º when connecting it to the new drive, so the dark cable is closest to the drive’s PCB. 1 2 3 4 • • D • |DATA||POWER| • • L • 5 6 7 8 This will fix the issue of the fans spinning up after a few minutes (technically, because the “HDD Proximity” sensor data was out of tolerance).

Just to be clear here both HD’s are Western Digital and are the same series and size that you are exchanging out correct? If so, the fact you still can’t get it to work correctly leads me to believe the issue is also within the HD’s firmware and/or this given HD does not have an active thermal sensor that meets Apples spec. FYI - Did you contact Apple to see if the HD was covered under warranty? They had a bad batch of HD’s in some systems and these systems have an extended warranty (call them with your systems S/N). If it was not covered by Apple you could also go directly to WD as they have a warranty program for there drives even if it was an OEM drive, that might get you a free replacement HD (http://support.wdc.com/warranty/index_en…)

Put inside the old thermal connector (in case you will put again your old seagate hd) 2 cables with connectors like these they use in windows pc’s for microphone on motherboards, put the black color on the first pin of WD hard disk closest to SATA connector In the lower (looking disc from above and connectors facing you) and the white colored cable next to black. Install fan control daemon and your finished. I played a lot with this and I find this is the best solution. Don’t worry about hard disc, its running at most 37c without cooling. You can go then to fan settings and make them run as you wish. I have them in 2000 RPM on all.

jump the connectors works fine after that. How can I jump the connectors? Jump the connectors means this:

Most upgrades seem to relate to the 27" iMacs, which have enough room for a thermal sensor cable as sold by OWC. Unfortunately there’s (as of yet) no way to upgrade the slow 5400rpm HD in a 2012 iMac. Even after 2 years of searching (on and off) I still haven’t found a way to either add a thermal sensor to an after market SSD, nor have I found a way to completely disable the thermal sensor with a hardware solution. The only possible solution so far seems to be to use a piece of software to adjust the HD-fan instead. @beneshelman; Do you have a link to, or maybe an explanation for us, on how you added the external sensor to solve the fans from spinning like crazy? I’m pretty confident in opening up an iMac (done it plenty of times), but adding cables that weren’t there is not something I have experience with :)

I replaced my original HD in my Imac 21" mid 2010 and experienced the fan problem (full speed) as well. Instead of going into a new disassembly and error and trial exercise to quiet down the fans, I got me a license on the HDD fan control. That worked very well and now my Mac is not noisy any more. I rely on the program statement that temperature now is controlled through the S.M.A.R.T technology for sufficient protection of my IMac. 16/12/2015 Roald

Great thread - very informative! I used an eBay sourced optical drive sensor (transistor type) from a different iMac and taped it to my new hard disk. These seem to be less expensive on eBay than those sold as HDD temp sensors. Worked perfectly with no need for additional software.

Hey, I realize this is an old post.However, I have learned some things while trying to replace the hard drive on a 2011 IMac 21.5". First, the hard drive used must support SATA connections of 3Gb/s, as this is what the model I am using uses. Anything else will result in a white screen with a flashing question mark folder. Secondary, I overcame the thermal monitoring problem by using the equipment already provided. The hard drive in the mac had failed but the board still had a functional thermistor on it, allowing me to unscrew the PCB from the old hard drive and keep the 4 pin cable attached. Then i tucked this PCB under the new drive and only plugged in the SATA connections into the new drive.

I found that when changing the HDD to take the pcb board off the new drive and remove the upper section of the plug with needle nose pliers. This allow the tab on top of the temp sensor to fit into the plug of the new drive. If you look at the original drive you will see the notch that allows the plug to be inserted. Notch is like the notch on ide cables. I just did this on over 100 2010 imacs and have had no issues. Dept of Education Imac tech

Quickest solution. Remove the previous hard drive’s pcb, connect the sensor into that board and tape it around to prevent this board touching to any live component, tape the old pcb behind the new hard drive. Done in a minute. You don t need transistors, jumping wires, soldering skills or a fan control software. (Some other people posted it too)

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Hi my friend! Of course the drive failed because of the bad construction of cooling in these desktops.I cant understand what Apple thinking when was making these all in one machines..Maybe is only for Antarctica? :) I have seen temps in hard drives more than 50c and continiously..They cant last like that..The most is 37c at continuous operation..Of course Western digital hd’s can last longer than any brand( not the blue). The only solution is to install a third party software to control fans and the only one that is working as i said some months ago is : http://www.derman.com/iMac-Fan-Control Dont search anything else is not working like this at least for my mac. then join the two point connector together itsself. The next thing is to put the hard drive outside the aluminium case and put an fan from desktop tower on it with a case for external drive and then your hd will be work at most in 32c. That’s it.