Great app, but I see you've stumbled across the same bug as me. Unfortunately, you've also gotten a lot of useless answers from our fellow forum users. *sigh*
First of all, about that bug:
If you play around with the Auto, Manual, and SMART buttons, the app will get "stuck" at the incorrect fan speed (as you show in your screenshot). In my case, where I had experimented with setting the Manual speed to 1300 in the past, I can reproduce this bug by simply switching from SMART to Auto and back to SMART again. Rather than settling on the 1100 RPM set in the low temperature bound, mine is now stuck on 1300 RPM. In your case, I'm willing to bet that you have experimented with setting the Manual speed to 1500 RPM at some point in the past.
To fix this and get it back to normal, make sure SMART is selected, then tweak the lower temperature bound to a value lower than your ambient temperature of 38 (for example set it to 30), and wait for the fan to speed up. Now just set the lower temperature bound back to 45 and it will settle down to 1100 RPM again.
(As I'm sure you've already noticed, setting SSD Fan Control to SMART, followed by a reboot, will also solve this)
A brief explanation of the settings:
To answer your question about what 1100 RPM @ 45C means, it's easier to just explain how the values the lower and upper bounds work. In your case with values of 1100 RPM @ 45C and 5500 RPM @ 70C, the fan will behave as follows:
If the temperature reported by your drive's SMART data is at or below 45 degrees Celsius, the fan will spin nice and slow at 1100 RPM. At that speed it's difficult to even hear the fan. Nice. If the temperature is at or above 70 degrees Celsius, then your fan will spin very fast (and loud) at 5500 RPM. At temperatures somewhere between 45C and 70C, your fan will spin at some speed between 1100 RPM and 5500 RPM.
If you set the temperatures too low, your drive will be nice and cool, but your fan will drive you crazy.
If you set the temperatures too high, your fan will be nice and quiet, but you run the risk of cooking your drive to death.
Are your settings good settings?
Whether your values of 45C and 70C are good for you depends on several factors, the most important being the manufacturer's recommended operating temperature for your particular SSD (or hard drive). You don't want to run the drive so hot that it cooks itself to death after just a year or two. You also don't want to run the fan too fast for extended periods of time, or you risk wearing out the fan's bearings (probably not very likely, but something to consider). Finally, you need to live with this thing - if the fan is too loud, it's not going to be very pleasant to sit near it.
I have mine set to 1100 RPM @ 30C and 5500 RPM @ 70C, because I want to give my drive (a Seagate SSHD) a little extra cooling, while keeping the fan relatively quiet. This results in a temperature of somewhere between 45 to 55 degrees, with fan speeds around 1200-1400 RPM, depending on how much work the drive is doing, and the ambient room temperature. If the room is quiet, I do notice that the fan is on, but with music playing (even at low volume) I don't hear the fan. Very nice.
Final Thoughts
For us with Late 2009 27" iMacs with aftermarket drives, this app is perfect. Not only does it prevent the fan from running at a crazy speed of 5500 RPM, it lets us fine-tune the temperature we want the drive to be at. (Note that this old model of iMac didn't ship with an external thermal sensor taped to the drive, rather it got the temperature info directly from the drive, via a special cable connection). So unless your SSD is lying about its SMART temperature data, this app is all you need!
