Also look at 'room temp. sensor', ..there is a little grille for this on the lower fascia [near your left knee]
This checks the temp. and adjusts the system accordingly, apparently this must be clean.[As well as not faulty!]
If you cannot switch the blower off at all, suggest the relay for the heater is stuck 'on'.........guessing...
as is 'before' the transistor for the aircon.
if you fix it please give update so we all learn!!