A/C Leak: What is this brass valve on the accumulator/drier?

I replaced the drier/accumulator on my 1996 XJ and all the refrigerant leaked back out. I traced it to this brass fitting (lots of oil/dye dripping from it). It felt loose so I tightened it and it sheared right off, but it was open on the end and seemed to have another valve underneath it that hisses when I touch it. Any idea what this is? Is there a way to tight it or do I just need to buy another unit?

Photo: https://imgur.com/a/iRZkK12

Where did you buy it? That fitting is for the low pressure switch. The other side should be the high pressure relief valve.

What sheared off? Can you post a pic?