Q: AIR CONDITIONER IS BLOWING HOT AIR. Does this mean its the compressor necessarily?

Hello. I will be glad to help you with your Murano. A common cause of a "no cooling" condition is the system is low on refrigerant, however, inasmuch as your car is only 6 years old, if the refrigerant level is so low that the compressor won’t operate (low pressure cut off switch accounts for this) you probably have a leak that will have to be repaired.

If the system is not low on refrigerant and the A/C compressor is operating (a Mechanic can at least see if the clutch has engaged) first thing to check is whether the heater valve and/or blend door are possibly stuck thus operating the "heater" at the same time as the A/C. If that checks out OK, there is a basic diagnostic to get to the root cause: Via gauge readings, if there is adequate pressure in the system and yet the compressor is not running, there could be an electrical problem with the compressor clutch or wiring to the clutch.

The compressor can be forced to run by energizing the clutch directly. With the compressor running, a further check of the charge level is possible because you would be able to get low and high side readings of the running system. If the compressor runs when commanded and there is adequate refrigerant (as reflected in hi and lo side gauge readings), there is an electrical issue that has to be repaired. That could even involve faulty high and low pressure cut off switches in the refrigerant circuit.

If in the diagnosis, the system turns out to be "empty", that is gauge readings show no pressure, don’t bother re-charging as you have a substantial leak and the system will have to be opened up and repaired, with a new drier installed, prior to evacuation and recharging. The overall scenario or problem you are describing is fairly common (unfortunately, inasmuch as no a/c can be brutal in some climates) and thus I encourage you to simply schedule a diagnostic with YourMechanic because they will get the root cause identified quickly and then explain your repair options.