Volkswagen Repair: Broken A/C, r134a, 12oz

Question
My A/C stopped blowing cold air.  It has been working for a while and it suddenly stopped blowing cold air.  I usually turn it on throughout the year. I have a gauge in which I measured the PSI on the low service port and it shows 45 PSI.  What problem could it be?

Answer
Thank you for your question.  45 PSI sounds low but the real question is what is on the high side. Normally, the low runs around 60 to as high 100 PSI.  The problem could be a couple of things the low side block that goes into the compressor could be blocked or a block in the high side.  Or just simply needs to have more R134a added.  Usually, it just needs to have one 12oz can added to the system.
Hope that helps