I personally still feel squeamish about attaching gauges to the system -- (what if the schreader valve decides to stick open?... or I get a bad connection?) Plus you bleed off a little refrigerant into the manifold lines with each check.

I vote for leaving the system alone until you notice a difference in a/c performance... like you said, when the compressor cuts out from the low pressure signal, or the vent temperatures start getting warmer. This system works best when left alone.

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95 E320 Cabriolet, 159K