Confused about AC connections

[88911coupe]

OK...still trying to figure out why every time I vacuum and recharge I quickly get to very high pressures and ac performance that's half assed at best. Charlie G suspects I'm getting ambient air in the system which makes sense. SO...i decided to try and duplicate a system someone came up with using ball valves to shut off the hoses and pull a vacuum between changing cans of r134. Seemed simple enough...went on amazon and got three short hoses with ball valves. Opened em up and only ONE seems to be the right size as far as the "female" connection. WTH? the other two the threaded "female" barrel is substantially larger than the one that fits all the connections.
Can someone explain what I need to order to get this to work?
Note that the inner part that actually seals is the same size as the one that works...only the outer threaded female barrel section is larger on two of them.
Hope this makes sense....
I'm also trying to find a "Tee" connections to hook these up but now am confused as to what to look for...can't seem to find any an any stores, will have to order online i guess.

[Discseven]

Ordering fittings online... great for someone who knows necessary fitting specs/dimensions. For others---including self---best way to get a manifold configured with ball valves, fittings and hoses is to take manifold to an AC place that sells technician supplies. There, one can configure entire system with parts in hand. Even if a retailer is a long distance drive… its worth the drive.

System below is designed to pull a vacuum in AC and manifold system right up to refrigerant tanks's valve. “T” just off manifold allows vacuum and refrigerant source lines to be simultaneously connected to manifold. Hose with the straight path into manifold is refrigerant line. Planning where a vacuum pump and refrigerant source will be positioned relative to manifold allows appropriate length of hose to be chosen for each.

[Discseven]

Believe "T" is standard on most manifolds.

[kuehl]

Ideally, the best manifold 'system' is a 4 valve, 4 hose.
This would include separate valves and hoses for: low, high, vacuum and refrigerant;
and is less likely to have propensity to leak because of fewer connections and valves as opposed to 'adding' on extra hoses and valves.

A 4 valve manifold allows you to pull a vacuum on the refrigerant line while your refrigerant container is attached (the refrigerant container's valve is closed at this point).
You are pulling a vacuum on this line rather than trying to flush the line of its ambient gases using refrigerant.

In terms of manifold, hose and fitting sizes, you have to identify what you are connecting to, typically you can encounter:
1/4" MFL
1/4" FFL
1/4" (7/16"-20)
1/2" Acme, F or M
3/16" FFL
3/16" (3/8"-24)
and a few more.

Again, investing in a 4 valve 4 hose manifold system is the wisest choice.

[kuehl]

Entry level analog 4 valve manifold




Digital 4 valve manifold



The benefit of a 'digital' manifold system, that has a transducer which allows vacuum measurements in microns, will become apparent to you when you run into pump or system vacuum issues. Using the micron transducer to test your pump's capability, test your line set and manifold for leaks, test your vehicle system for leaks, and to insure the system is pulled down to a sufficient vacuum level.

[88911coupe]

OK...I think 2 the larger female hose end connectors are 1/2" ACME but not sure. I measured the inside diameter of the female connector end and it's .44". This is measuring the "peaks" of the threads, if that make sense. The other/male end is the same on all three, which I think is 1/4"....not really sure what the 1/4 or 1/2 nominal name is referring to.