Q: How to remove and install the heater control unit in a Nissan Altima?A: First of all, disconnect the battery's negative terminal. Use a tool to pry up the grille from the vent. Remove the trim panel and A/C switch screws. Disconnect the wiring and remove the A/C switch. Remove the two side brackets to fully remove the A/C switch. Reconnect the battery and perform re-learn procedures.