That is Reversible Catch All HPC-163-HH used for? I think it is a liquid line filter dryer. But what is its purpose?
It's used to to filter the ref. in the line sets. On burn outs two can be installed one on the smaller line and one on the larger line and the one on the larger line removed as it catches acid and begins to fill the filter up with debris. The reasoning is it keeps anything from ever entering the compressor to cause damage again. The acid causes the burnouts.
Your best bet to insure everything is clean and will work properly is to have the entire line set replaced with the proper size and the compressor and associated parts replaced.....the evap coil cleaned....and two filter driers for the lineset. After it runs for a short period the larger filter dryer should be removed.