[joe123]

How come all new R134A AC systems use O-ring fittings. As best as I can tell all R12 AC systems used flare fittings (45 or 37 degree??). Is there a technical reason for this? If an older r12 system can be retrofit to R134A then it doesn't seem like there is any reason not to continue to use AN fitting.

The reason I ask is because I'm working on my AC now and need fittings. The Aeroquip O-ring fittings and hose are $$$ and selection is limited. Any reason to NOT use teflon hose and fittings (like those from Earls or Russell).

[75gmck25]

My '75 GMC truck had quite a few O-ring fittings in the stock setup. For most I just switched to new green O-rings when we switched hoses. I also put in a new condenser that had metric size fittings, so they just put metric O-ring fittings on the end of that hose. All my hoses were custom made because I used a new parallel flow condenser and lightweight compressor, but the hoses only cost about $150, with labor.

I don't remember fittings being a big expense when I went to the A/C place to have hoses made. The only exception was that the stock fitting on the GM evaporator was large diameter, but the original fitting then necked down to a much smaller hose size. The guy just brazed two fittings together to make a step-down adapter that allowed the large diameter hose fitting to work with a smaller diameter hose.

Bruce

[joe123]

Reading through the Vintage Air pdf and they specifically state not to use AN fittings. No explanation provided.

Now I'm really curious.

The only two things I can think of is A: the R134A molecule is so much smaller than R12 it's able to sneak out the fitting. B: AN fittings may loosen over time with vibration.

[joe123]

Excellent source of information...

Red Dot AC

[Joe G]

Originally Posted by joe123

Reading through the Vintage Air pdf and they specifically state not to use AN fittings. No explanation provided.

Now I'm really curious.

AN flares are 37 degrees. Refrigerant flares are 45 degrees.

Personally, I hate A/C flare fittings. When I have to use them, I use soft copper flare gaskets. Like these:


(link)

You should also lubricate them liberally (same goes for o-ring fittings), both on the sealing surfaces and on the threads. Use an oil appropriate for the refrigerant you are using.

Thanks for the link.

[302 Z28]

Flare fittings and "O" ring fittings are not specific to R12 or R134. The green "O" rings are specific to R134 systems. Personally I would not use flare fittings in a R134 system for the above mentioned reasons.

Vince

[Refer Mech]

O rings are used for round screen filter housings that house the screens that protect the freon passing sediments that might clog the orifice in the capillary or freon metering device before it enters the evaporator.
the freon meters the freon into the evaporator at a certain rate and amount....which is usually a small hole size... if theres no screens/filters the metering device would plug up...
However, the irony wins again.. most of these screens plug up, and they are installed in the hot liquid freon lines mostly, and theres a small square metal plate looking along the freon line... in that line is a pull apart screen filter inside.
When putting that back together, one will need a fresh o ring.
hope that helps some.