A/C related Question for DJ,Val,Jim K. anyone.

[Jim Fierst]

I just pulled the expansion valve in the 79 LBZ and I think it is the first removal from the original installation.. It had the "dog dough" stuff coating a couple of the pipes. 3 of the 4 lines are copper and double flared fittings and the 4th is a standard A/C male hose fitting. What was interesting is that the 3 copper ones had no O rings and the fourth (which I didn't origionally remove ) may not have either. In discussions with Allen L he remarked that there was a period when compression fittings preceeded O rings. These fittings were appearently sealing as I was pulling and holding 23 HG of vacuum. Can anyone verify that there were no O rings on these connections? The more important question is should I add them going back together?I am thinking yes.

[davidb]

Rule Of Thumb: compression fittings [have a brass ferrule i.e. beveled
sleeve] & flare fittings do not take "O" rings. Fittings that take "O"
rings often have a noticable shoulder or recess the "O" ring rests
on or in. Sometimes the "O" ring will stick in the female port i.e. pipe
is withdrawn, no "O" ring on pipe. Check that out. My 4 port/4 pipe
A/C drier? Two pipes took "O" rings, others no. All our A/C parts vary
[proprietary],no Rule Of Thumb there.

[Jim Fierst]

To have been technically correct I should have called them flared compression fittings , not flared or compression singularly. They are used in high pressure applications like in in the expansion valve of the Lancia. They are called flared compression because the sleeve that fits over the pipe pushes the rear flare and flat front compression face into the flat surface of the receiving device .. In this case the expansion valve. As most are made of copper the flat face derforms much like a copper washer. These were British in origin ( I think) There is a radius at the point where the front face meets the flat tube and a radius in the expansion valve.These probably make contact as well. I believe the design would support the use of an O ring. This type of fitting was prone to leaking because of the exactness required for a good seal and was superceeded in later A/C systems with O rings connections. I have attached a picture of the four fittings that screw into the expansion valve. It could very well be that the small inlet and large exhaust on the right had O rings while the inlet and outlet to the evaporator on the left did not. I would still like to hear from someone who has pulled one apart.

[davidb]

The one in your pic, top, takes a green A/C rated "O" ring. The bottom
pipe is an "interference" fit, nee compression. Will knows plumbing too.

[Jim Fierst]

Perhaps that is true but I would still like to hear from someone that disconnected all 4 fittings for the first time..

[davidb]

In my '82 LBZ I installed a new compressor, new hoses, new drier,
removed, flushed & replaced the exchanger in front of the radia-
tor. In my 76 Scorp I removed the entire A/C system. Make me
experienced, dunno? Maybe Will will chime in.

[Jim Keller]

Sorry, I would chime in, but I never paid any attention when taking them apart as I never had any intention of putting the A/C back in on ones I took apart and never had a problem there on ones I have repaired, it's always just been compressor or low on freon problems for me so far

[Will]

Sorry, Jim- I'm in the same boat as Jim K on this one. I do have the fische if you don't though, I can send you that and you can see if the o-ring shows up on an exploded diagram. This is the IMO the safest bet since nobody will really know if they took it apart "first" unless they are the original owner? Allen might know too, I know he did an AC retrofit on a Scorp and he may have had a Zagato system apart as well, FWIW. Good luck, Jim- sorry I can't help w/this one, I just don't know.

[davidb]

My finale. Once taken apart he will need NEW green A/C rated "O"
rings of the proper size where applicable. NO black plbg. "O" rings.
There, I've said my peace.

[Will]

My finale. Once taken apart he will need NEW green A/C rated "O"
rings of the proper size where applicable. NO black plbg. "O" rings.
There, I've said my peace.

AFAIK the ones you want to stay away from are Viton, and black (Buna-N) and HNBR (green) are both serviceable, wiith HNBR preferred for R134a?

[Jim Fierst]

Just to bring closure to this thread.. 3 of the four expansion valve fittings (to and from the evaporator and the suction take away) are all flared compression fittings that do not require O rings and will not seal if you try to used them. While the evaporator fittings are copper the take away is steel. The expansion valve itself is aluminum. I spoke with an A/C specialist and he said that he quit trying to make o rings work with compression fittings because of the significant numbers of leakers.