Originally Posted by JimBlake
What did you end up doing? I wish I could have known for sure whether you REALLY needed to drain the compressor or not...
And for CJITTY... The sight-glass method doesn't work for R-134a. Newer cars that came with this don't have a sight-glass. So if you've converted, you probably shouldn't trust it.
Really the PROPER method when retrofitting is to place a new compressor in, unless the old and new oil used are of the same type (i.e., a good amount of Toyota's old systems use POE oils and so do the newer systems, which also is compatible for the two types of refrigerants)
Newer systems DO actually have sight glasses, don't know why because it's point less, but they do.