Switch from 2 wheel to 4 w will not engage have replaced switch, Pump,

What is your question?

Switch light from 2 wheel to four wheel will not change does not go into four wheel drive have replaced actuator,switch,fluid pump, and transfer module still will not work. When it doesn’t engage It grinds. Also every time we turn off and back on the ac comes on

How long has your 2012 GMC Sierra 1500 had this problem?

3 weeks