Crazy! Use a hammer. J/K.It seams like you have done what I would do.Ill try and find some info on your problem?.I did have a heater that stuck on one summer in an old chevette.I used my foot to put the unit out of its misery.It sucked bad that winter though.

is your mode selector in the defrost position? this will activate the compressor even if the fan and a/c switch are in the off position.

i will pull the fsm tomorrow and see if their is any reason for this I will also check asist for any known incidents(bullitens). I do know the frontier ka24de a/c stays on once its turned to defrost and will stay on till the engine is cycled off then back on. even if the mode selector is moved it will stay on.but if the system is started with the a/c switch off, mode selector on any postion but one of the 2 defrost positions, this is the normal function of that vehicle's a/c system.