Yuck what a pain and it does not have any kind of device ID number in case you own multiple fans so it will mean a new serial port for every device so you know which device is sending the data. I would convert to using pure HEX and then simply learn what the hex for S is by using this
Here are some tips, set the serial binding to use ‘ISO-8859-1’ charset otherwise the conversion to HEX will not be correct and will confuse you. I believe the binding now allows you to set the charset as an option, have not used it since it was changed (?) so the following post may need to be adapted slightly. Note the post was made in 2015 so if you work it out be sure to post what works to help others.