I have old electric heating/AC unit (about 30 years old) and it works fine and monthly bill is not high like $90 per month. I try to set the temprature not very cold or hot either. It is a 2 ton unit and I live in condo in sunny south. Any way more or less every year I had to call call AC service guy to add more Freon. He tells me that he can't tell from where Freon is leaking. He never bothered to even look as well. He tells me that in my building AC (Freon) pipe go below the building and build has concrete floors so it might be possible that Freon line has been cracked and Freon is leaking some where underground and there is no way to fix it. Or unless I want to install new pipes which will go outside of building to my unit but this is impossible as it will hurt the building image and condo board will never allow it. How do I overcome that? I hate to spend $75 ($40 for Freon and $35 for maintainence check up like cleaning the coils, oil the motor, check wiring) every year on that. Even If i replace this unit with a new unit I will not save much on electricity as new unit will only save me $300 - $400 per year and it will take like 15 -20 years to recover the cost + problem of leaking will be still there. Any suggestions what to do?

ok a/c quit blowing cold, all parts appear to work. called hvac guy and well he was little to no help, upon doing some additional research and doing some research on a hvac forum the consensus is that the valves may be going bad. has anyone had this happen? if so what is the repair? what should i prepare myself for cost wise (roughly) ? after dealing with the hvac guy today (it was a joke) and calling for another one to come tomorrow i just want to arm myself with info and be somewhat prepared. thank you for your advice.