In my limited knowledge of AC systems, I always assumed there are two ports in a system, one in the high side and one in the low side. In the instructions for the R134a "retrofit kit", Volvo has a new port which installs by the dryer (high side?), then states that the two ports in the compressor can be sealed as they are no longer needed. I suspect one could evacuate and charge the system through that one port with the compressor off, but it appears that all the diagnostics on an AC system are based on the system running and with connections on both high and low side. Am I missing something? By the way, I got a later R134a compressor from a later Volvo and it does not have ports in the back.

Thanks in advance to those of you sharing your knowledge

Charlie
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