I'm trying to control my thermostat(Venstar T1700) through PLM #2413U. I am able to get the status of the thermostat through my Perl script but I am not able to change the thermostat mode through the script. For e.g. when the thermostat is in off state and when I issue cool on command, I get the following reply and nothing happens.
If the thermostat is new enough to be an I2CS protocol module. It may require an Extended Insteon Message as LeeG pointed out and have the Checksum calculated.
If I read your response back from the module correctly. Your PLM is an address AA.AA.AA. That is the Developers PLMs ID. Are you a Developers Group Member? If you are the cmd2 of fd is documented in the I2CS Developers Notes.