I am looking to get some pressure readings on the A/C system in my 1991 z28. I have a dual gauge manifold that has 1/8" npt connections and hoses. They hook up just fine to the low side however they don't fit on the high side. Is there an adapter available so I can leave the schrader valve in and get some pressure readings. Does anyone know what the thread type is (threads per inch or something?) I also have 134 quick couplers that came with my gauges, and I wouldn't mind putting a male quick coupler on the high side, however I would like to leave the system pressureized.
Thanks

 

Yes there is an adapter. I have several of them. No I don't know offhand what the thread pitch is; but they're all the same, so if you get a high side adapter, it will have the right threads.

However, my advice would be, if you're that unfamiliar with A/C systems that you don't know about the adapters, don't touch the high side at all. Just leave it alone. Messing with that port isn't necessary for the majority of system service, and you'll probably end up doing more harm than good by dinking with it.

 

If you want to just read pressures youll be fine tapping into the high side of the system. Just make sure that if you add refrigerant to the high side you have the engine off. Otherwise the compresser will pump refrigerant into your filling container. It will only hold so much before it goes boom.