DanG wrote:
Simple: at the outdoor unit there will be 2 pipes. One large,
one quite a bit smaller. Check while the unit is running on a hot
day. The large pipe should be quite cold to the touch - depending
on atmospheric conditions it may be sweating a bunch or even
showing a touch of frost. The small pipe will be almost hot
enough to burn your skin.

It is just as common for the small pipe (the liquid line) to be at or
close to ambient temperature.