Don't you just love 134a, It's the best thing since sliced bread !!

As stated above waxes capilery tubes wonderfully.
A tip for what it's worth, braze a piece of 1/4 copper to the end of the capilery about 6" long with a 1/4 fitting on the end, spray some wd40 into the copper pipe, connect line to nitrogen bottle and blast away, don't forget to remove sution line from compressor, not that I think the small amount of wd40 will do any harm to compressor. Nomally clears capilery of most junk

Good luck

Mr Cool