For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

California Proposition 65 WarningAir Conditioning O-Ring Seal Replacement
Removal Procedure
Disassemble the A/C refrigerant components. Refer to the appropriate
repair procedure
Note: Cap or tape the open A/C refrigerant components immediately
to prevent system contamination.
Cap or tape the A/C refrigerant components.
...
Rear automatic air conditioning system
Basic information
The rear automatic climate control system in the Nissan Armada is engineered
to provide enhanced comfort for all passengers, especially those seated in the second
and third rows. When the front air conditioning system of the Nissan Armada is activated,
the rear system become ...
System temporarily unavailable
When the Nissan Armada detects that the radar sensors are obstructed, the system
will automatically deactivate to ensure safe and reliable operation.
A warning message reading "Unavailable Side Radar Obstruction" will appear in
the vehicle information display, alerting the driver that ...