I have a 2 ton unit (very old - The Smithsonian is asking for it!) and the compressor just shorted. The line is 1/4 inch. The technician that came out said that all newer units use 3/8 inch lines. He also said you could put a newer unit designed for a 3/8 inch line onto to the 1/4 inch line, but that the "head pressure" would be greater and the compressor would fail quicker.

Does this make sense?

For various reasons (contemplating an addition) I would like to just get a used unit and have it hooked up and make it through this year. Any thoughts?

Thanks!

If you are looking at a used unit then hook it up as it is. If you are going to go with a new unit then the lines will need changed

In my opinion, your options are fix what you have or spring for a new unit. Any used unit will cost just as much to install as fixing what you have or will likely have its own headaches.

Maybe consider replacing the bad compressor, instead of installing someone else's used (how knows) what could happen to the used unit