Many years ago I had the my R 12 system converted to use R 134a, on my 91 ford Ranger. At the time, I took it to a reputable shop for major repairs to my AC and they said that this would be a good time to also convert it all over. Fast forward to the present: Even thought the low side had a 134a fitting, I just noticed that the high side still had a R 12 fitting. For some reason they didn't change the high side one. I just want to know if maybe I'm missing something; certainly this can't be normal. How is it possible that this could happen?

 

It would have cost you more

And all AC shops would have the adapter to test or service it in the future, but maybe not a DIYer, lol
And if it was "many" years ago they were right, you didn't really need it changed

 

LOL!