Hello, I am needing some advice. My son's home has a trane heat pump which is 15 years old maybe. About 6 months ago he told me that the blower inside runs all the time but the heat was fine but fan never stops. I called a tech out and he checked everything and said that we had a leak at the valves where the lines go to the outside unit. He said that he could put some freon in to bring it back to proper level so the heat pump would work again, but that if it leaked out again they should fix the problem which he said was the valve needed replaced. He used a sniffer to find the leak and showed me the oily dirt around the valve and said that was the problem area.
Now that we are in the air conditioning season , the fan is running all the time again.
1. Does this problem sound correct and the fix make sense?
2. He and me can't afford a new unit so I would like to have repaired if it's a good fix and makes economic sense rather than replacement of the whole unit.
3. It has the r22 , do I continue to use that type or is it like old cars and you upgrade to something else if you have to work on them.

Thanks for any advice on this dave