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Fittings for nitrogen pressure test

idickers on Thu August 22, 2013 11:57 AM User is offline

I'd like to pressure test my a/c repairs with nitrogen prior to charging the system, and am running into problems finding an adapter to connect the output from my regulator (1/4" male pipe) to the yellow hose on my manifold gauges (1/2" female acme). I've struck out calling local refrigeration supply houses, and wonder if anyone can suggest a source, or a combination of adapters to get the job done. It looks like the adapter I want is 1/4" female pipe-to-1/2" male acme.
Thanks for any suggestions!

webbch on Thu August 22, 2013 2:22 PM User is offlineView users profile

I'm sure such a fitting exists...somewhere. If you can't find any other way, it's easy enough to find 1/4" male pipe to 1/4" male flare fittings at most hardware stores. I haven't looked much for 1/2" acme. Then stick an R-12 to R-134a adapter on top of that (1/4" female flare to 1/2" male acme).


this is also an option, but you'd have to cap off the port you're not using.

Leggie on Tue August 27, 2013 4:09 AM User is offline

Quote
Originally posted by: idickers
I'd like to pressure test my a/c repairs with nitrogen prior to charging the system, and am running into problems finding an adapter to connect the output from my regulator (1/4" male pipe) to the yellow hose on my manifold gauges (1/2" female acme). I've struck out calling local refrigeration supply houses, and wonder if anyone can suggest a source, or a combination of adapters to get the job done. It looks like the adapter I want is 1/4" female pipe-to-1/2" male acme.

Thanks for any suggestions!
In North America, majority of small HVAC/R applications use 1/4-20" for almost all refrigerants on all ports. This is the R12 cylinder thread for you car only people.

Does your regulator have the 1/4" flare (R12 tank) or 1/4" MIP? These are different. If you have a MIP, you use a brass 1/4" FIP to 1/4" male flare fitting which is available in ordinary hardware stores.

If it's 1/4" flare or you just created a 1/4" flare with the above setup, you use a 1/4" flare to SAE adapter. Search eBay for "sae 1/4 adapter". This is a very common adapter, because 30 lb 134a cylinder is available in SAE ACME as well as 1/4" flare. The former is sold through automotive distribution channel while the refrigeration channel sells the latter exclusively. Since the contents are identical, this is a common adapter.

Is this just a one time thing? If so, you don't need to buy an adapter. Just hookup the high side hose directly the the regulator. Unclip high side, then observe pressure bleed from low side. The system will equalize, ya know.

Edited: Tue August 27, 2013 at 4:10 AM by Leggie

mk378 on Tue August 27, 2013 11:29 AM User is offline

I've never seen an adapter that can do this in a single piece. You would start with the "vacuum pump adapter" to get to 1/4" flare, then a widely available flare to NPT fitting to get to pipe threads.

https://www.ackits.com/pc/82031/Vacuumpump/82031+-+Vacuum+Pump+Adapter

There also exists a simpler vacuum pump adapter which instead of a tee is straight thru to Acme only, though I didn't find it on the AMA site.

Another option like Leggie said is to put an ordinary port converter (as used for retrofits) on the flare fitting from the regulator. Couple one of the manifold hoses to the port converter and the other one to the car. Leave the yellow hose blanked off. Open both manifold valves to let the nitrogen go through and fill up the car.

Leggie on Tue August 27, 2013 2:57 PM User is offline

Quote
Originally posted by: mk378
I've never seen an adapter that can do this in a single piece. You would start with the "vacuum pump adapter" to get to 1/4" flare, then a widely available flare to NPT fitting to get to pipe threads.

I'm not sure what kind he was referring to by 1/4". male NPT(MIP) or male flare.


Quote
Another option like Leggie said is to put an ordinary port converter (as used for retrofits) on the flare fitting from the regulator. Couple one of the manifold hoses to the port converter and the other one to the car. Leave the yellow hose blanked off. Open both manifold valves to let the nitrogen go through and fill up the car.

Not quite what I meant. Hook up the gauges as usual. Keep both closed. Disconnect high side from the gauge side, then hook up up to nitrogen. Pump nitrogen into high side. As you pressurize, you should see the pressure on low side rise fairly quickly, then slowly stabilize. If it doesn't, you might as well giving up leak testing, because it means the path from high port to low side is clogged.


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