Where do you charge the rear air on 2001 navigator?

The 2001 Lincoln Navigator doesn't have a separate rear air conditioning system that requires a dedicated charging port. The rear climate controls are part of the overall vehicle's air conditioning system. Therefore, you don't charge the rear air separately. If the rear air isn't working, the problem lies within the main AC system itself (low refrigerant, compressor failure, blower motor issue, etc.) and requires a professional AC technician to diagnose and repair/recharge the entire system.