Hi did a few of these when I worked at lexus main dealer a few years ago. Underneath the car on the ns there is a plastic cover and the rear a/c pipes join there ( 2 unions one 19mm and another 24mm if if I remember correctly ) we used to cut the pipes further back towards the rear and remove the front pipes and take to a local a/c specialist who soldered them up then refit the pipes(leaving the rearmost pipes in place ) and regas the system. Only the front a/c works but it got cold enough. I still work on one of the ls430,s and a/c still works ok
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