recharge kits are fine as long as you dont expect the most from your a/c system, if the system was empty that means there is a good sized leak plus if you dont have a guage you can easily over charge the system and hurt the compressor or other parts of the system,also when all the freon is gone and the compressor is running that leak becomes a inlet for air. next thing you know you have a onboard air compressor ... air in the a/c system will decrease your space for freon . the proper way to recharge the a/c system is to pull the system into a vacuum and this process is done for approx 15 min to remove moisture and air in the system. even with a full charge moisture and air will cause the system to not cool properly.