if it was mine and i could keep it going by just adding a pound of freon a year i would continue to do so.

Same thing happened to me. I have a 10 year-old 3.5 ton York. Last year the AC stopped working, the technician added freon (old type) and did not mention about a possible leak. It seemed the freon did not last very long, since the winter it did not work well Most of the time, the system ran on the aux. heat. This Summer the AC stopped again. The same technician came and he added freon plus dye. This time he said there is a leak (likely in the air handler).

The first service call was $150 and the second was $168 (dye was injected).

The technician did not recommend a new system, but I have had several quotes ranging from 8k to 6k for a new system. Have not decided what to do yet. With $150 a year for freon and if it lasts through the winter, adding freon is not bad choice relative to a new system or replacement a new coil.

Replacing a coil in the handler would cost $700 part and labor.

"Replacing a coil in the handler would cost $700 part and labor."

Finding a coil to match a 15 year old system is not going to happen.

This would leave you with a mismatched system and may actually increase bills.

If you switch from an orifice to a TXV it might reduce bills, but there is no way to be sure before installing the change.

so a leak in the coil in the air handler can't be not repairable?

I called and talked to the tech. about his plan for my heat pump. He told me that if a leak is in the coils (in or out), he has to find a replacement. I might take 3 months; heat pump coils are not readily available??? even to match a 10-year old York

I decided to have my former a/c technician do the maintenance again even though he had switched companies. He explained that he and most of the other techs had left his former employer because the new owners were pressuring them to sell new systems.

After recharging my system the two previous years and saying I needed to start thinking about a new system because of a leak...this time (a year later) he said the system did not need more freon. Hmmmm. I'll take the good news, though.

Any leak can be found and repaired, it,s simply a matter of how much labor will be required. The leak detection system using a powder that glows under black light allows almost any small leak to be detected. However, the cost of evacuating the unit and repairing leak can be expensive and many times as long as only a small amount of freon needs to be added yearly the best course is to leave the unit alone. The coil can be replaced, while it might be difficult to get an exact replacement, universal after market ones are available and using one would create a slight mismatch, but I doubt you units effeciency would suffer much. We have replaced many and never had a problem. My suggestion if only a lb of freon is required, keep adding it.