Arrived to unit not cooling properly. Client has had unit freeze up before but never charged up. I proceeded outside and confirmed the unit was low on refrigerant. The system takes R410a. I gave our clients the option to charge it up with Freon but I explained that there is no guarantee or warranty on the Freon. We also discussed how there is a leak present Most likely in the evaporator coil. They declined the Freon charge at this time. They are aware the system takes about 7.5 pounds of Freon total. They shut the unit off and will continue to run is sparingly.