Pressure Test Rig for R12 Rebuild
 

AC gurus -

I have read through all the threads and I'm aiming to hook up my welding gas cylinder to pressure test my AC system.

My question is: What connection do I get to go from the AC hose (R12 flared fitting) to the gas regulator - 1/4 straight threads.

Grainger / McMaster etc. give me no options.

Help :-) I'm trying to do it right.

Your Nitrogen cylinder ?

I am not able to visualize where you are needing this connection to span.....
Do you not need a hose from the output of the Nitrogen regulator... to your R12 manifold ?

Sounds like he is going to substitute the welding gas to me.

Find a hose supply store, tell them what you want to connect and how long and they should be able to help. You may have to shop around a little.

hoses in Boston

I'd try AIT first.

The AC side fittings are generally SAE 45 degree flare for 1/4" tubing. ( not inverted flare brake tube ) Any decent auto parts or home center will have something.

As for the regulator side, most use a male thread ball seat fitting that I can't recall the name of. A welding supply should have this. If your regulator has a hose barb with a clamp, attach a piece of at least 100 PSI working pressure hose. ( Fuel injection hose , Gates Lock On type hose works also. )

Bought my N2 regulator rig at the welding supply shop (it's a 'Turbo Torch') and bought a brass fitting (SAE 45 degree) that was threaded on the non flare end (1/8NPT). I test at 100psi - no more, no less. The fitting fits R-12 charging hose for auto applications.

That is a good answer..

' a welding gas ' may not be safe for this.... even Oxygen under pressure can cause an explosion..
let us know more..
we do not want you to get hurt..

Since the argon component of the welding gas has a smaller molecule than nitrogen. I use argon for pressure testing.

Argon and Nitrogen are noble gases and great for pressure testing an AC system..

' Welding gases ' is too broad a term to endorse because even something which might seem safe.. like oxygen ... when under pressure in contact with any oil can cause an explosion.. and of course the inside of an AC system has oil.

Hey sorry for thread abandonment - i need to go from the output of a regulator to the 1/4" flare male fitting to hook up to the charging hose on my gauge set.

i now see if i want to pressure test that Nitrogen regulators are standard 1/4" flare.

i was trying to sub in 75% Argon / 25% CO2 standard MIG welding gas since that's what I already have.

good suggestion on the custom built hose.

A lot of people use CO2 even though I do not like it... for no particular reason other than it is part oxygen ...

but I think Vstech uses it ....

Whatever things are directly hooked to your cylinders ... make sure they can handle more pressure than they contain..

and always wear goggles.... I have seen the faces of gauges get blown off...

It would be a good idea to define the gas ( in a later post our guy said 75 Argon / 25 CO2 )




This is so wrong. According the the Google machine, The six naturally occurring noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn)

Nitrogen isn't on the list









Dihydrogen Monoxide has oxygen in it also, so dumping some on a fire will make it flare up using your logic.

I use CO2 carbon dioxide to pressure test AC systems because I keep it for MIG welding rusty metal and as a portable "air" source for air tools and such. If you use it for inflating tires, it will leak out at a faster rate due to the molecules being smaller than nitrogen. ( Nitrogen makes up ~ 75% of the air we breathe. )

In HVAC/R work N2 is used because it is 1-inert, 2-cheap, 3-seems to "dry" the system.

CO2 can work, I used to use it, but N2 is drier which tends to give better results. I am sure Argon/CO2 would work for pressure testing, just make sure you evacuate completely then pull a 29.9mmHg vacuum in ambient above 70F (preferably in low/no humidity) for a good long time & you should get good results.

Hey Charlie Foxtrot, do you remove the valve core for faster evacuation and charge? How big a difference does it make time wise in automotive AC in regards to removing vs not removing the core?

Removing the core won't make much difference time wise in pulling a vacuum and when you remove the hose, air will enter the system negating the reason to pull a vacuum in the first place.

Long vacuum pulls are to let moisture evaporate / gasses to escape small voids ( like under bolt holes )

I am also a believer in LONG vacuum pulls... used to be Overnight was standard ...
ALSO ... if one has Nitrogen available ....

TRIPPLE EVACUATION is a standard procedure for HOUSE AC units.. where Flushing is not practical...

this means filling the system with ( DRY ) nitrogen.... letting it sit ( watch for leaks by monitoring the gauge pressures ) vacuuming it OUT..

and REPEATING THIS PROCEDURE...... three times is standard.....

the idea is that the very dry nitrogen will naturally absorb some moisture each time...and you can take it out by vacuuming ...

in re: Funola & 97SL320/valve core removal

In the R-12 days I used a tool that allowed you to remove the valve core w/o losing gas, and then replace it post evac & fill. Haven't bothered to get one for R-134A automotive ports.

Core removal made dye & oil injection easier, and cleaner. Long vac pulls are good if you have the time, but ambient temp is also very important. The purpose of a 29.9mmHg vac is to drop the boiling point of water to just below 70F. The modern technique is to have a micron gauge and to use your 'super duper' pump to pull down to 400 microns or so. I cheat. I use a heat gun while pulling a vac. I heat up all the metal bits to help the evacuation of moisture. If I am certain that moisture got into the system, I have been know to inject 90% isopropyl alcohol (small amount) & then draw it thru the system (reverse flow). The theory is that the alcohol will attach to the water and as a solution will evaporate more quickly while using vac & external heat.

Is this from personal experience having tested it both ways or just theorizing? There are people selling big diameter hoses who run tests with micron gauges hooked up claiming faster evac while achieving lower micron levels with Schrader core removed + big dia. hoses. Are they just trying to sell you stuff?

As for removing the hose and getting air in, that won't happen if you charge with the magic core removal tool (the type with a ball valve) + manifold gauges. Purge the charge hose before connecting to the manifold. When finished charging, install the Schrader core before disconnecting the magic core removal tool.

This is from what I know about CRT manufacture. A 35 / 36 / 38 " tube will achieve very near 29.9 In / hg within 3 / 4 minutes while pulling through a glass tube about 8 mm ID. To get down to CRT vac levels, it takes 4 hours while baking the tube in an oven to get the last few molecules out. This is a level that no one would ever be able to attain in an AC system.

A standard automotive ac system has a fixed volume that really isn't that large. Sure, in the first two minutes a larger hose may offer greater flow, however as the vac reading gets larger, there is less flow through the valve. When you hit anything near 20 in / hg , flow is minimal since there isn't much air in there. Time under vacuum is important to allow moisture to boil off.

On a vehicle with dual AC / bus or large commercial system, larger ports would help but that is beyond the scope of what we are trying to do.

what funola says in the next post is the cheapest way.

Getting a nitrogen regulator for a gas canister is the off the shelf way.

"Trying to make the adapter costs the same amount."

Same amount as what? I have a 20 lb Argon tank and Argon shares the regulator as Nitrogen and Co2 afaik. I took an old AC manifold hose, cut the fitting off one end and hose clamped it to the regulator barb. Voila, instant adapter.

I did not think of that brilliantly simple solution. :-/

I retract my previous post---thats the way to do that.

Argon and Nitrogen use the same high pressure side regulator fitting: CW male thread , rounded pressure fitting ( CGA 580 ), CO2 uses a female thread , flat face fitting with sealing washer ( CGA 320 ) https://www.concoa.com/cgachart.html

This is all becoming more complicated than it needs to be. Locate a 1/4" female AC fitting with a valve depressor, adapt this to a 1/4" hose barb. ( maybe larger barb depending on what you find the the welding place below. )

Go to a welding supply house, ask them for a fitting that screws into the low pressure side of a MIG welding regulator , they can even supply some 100 PSI min hose and crimp both ends of it.

You now have something to pressurize your AC system regardless if you use Argon or Nitrogen.