I doubt very much that your alternator has temp control. Unless Volvo has recognized that to be a problem and snuck in on there. But probably not. The stock engine
alternators are normally fine for keeping your start battery
charged and may be keep some charge on a lightly used and/or very small house battery
bank. And that is before you put any heavy, continuous load on them from a serious amp hog. You didn't say how many amps your watermaker
will draw though so if it is low it won't matter.
But in any case, a temp sensor on your alternator is to give data to the alternator regulator so it can manage the output of the alternator, and not the alternator per se. You would need a smarter regulator than what comes with your Volvo, and one that supports alternator temp sensing.
If your loads are big, and/or your battery usage is big, then you will surely need a bigger HD alternator, one that is designed for heavy, continuous output. Volvo will not have put one of those on a stock engine
. But exactly what size and mounting considerations, etc., are dependent on what you want to put on. But it will need an external regulator.
N.B. I just looked up the engine specs. Your motor
comes with a 115A alternator which is a reasonable size for normal charging
. It will be fine for "normal" usage with a moderate battery bank and moderate usage but it is not designed, necessarily, for recharging deep cycle batteries in the best way. You really need to get a smart regulator with a temp sensor and ability to manage the heat on the alternator for running the inverter
. And it may save your alternator for just recharging your house bank as well.