If you are referring to the roof top A/C as the "cabin air", they are generally not re-chargeable. There are no hookups for refilling them with coolant like a dash air would have. What do you think it need attention? Not cooling? Sometimes that is as simple as a good cleaning of the coils and change the A/C filter. Be a little more specific with your "problem" and type of A/C to receive better answers. Good luck!