chip-powell

Last year, my biggest project was replacing most of my air conditioning components (compressor, evaporator, POA, drier, O rings), and converting over to r134a. Everything went great and I had ice cold air the rest of the summer.

She went into storage for the winter and now that the weather is hot again I turned on the a/c...and got hot air blowing on me! I figured that a leak must have sprung up some where so I took her up to my local garage so that they could test the system...and the results were...no leaks.

If a car is in storage and not being used for months, will r134a evaporate, or maybe seep out somehow?

I'm stumped.

Koda

So, what was the pressure in the system at the shop? AC systems will leak to a certain degree. What I would diagnose the system as, you did not run the compressor all winter, and the O rings, which need to be lubed, leaked. Other contributing factors may have been an incorrect amount of R134a put in (as in low), and oil in the system.


R134A is cheap. Charge her up and run the car every month in the winter. Every other system on a car can sit for a while, provided good gas. AC systems need circulated. That being said, running the car in the winter causes its own issues, like improper warming up and such. I like to start them, run them to warm, run them back and forth in gear, leave them on different spots on the tires, cycle the AC, run the heat, etc.

Olds64

Did you upgrade the hoses when you converted to r134a? If you used NOS hoses they probably don't have a barrier lining. It's my understanding that AC hoses need a special lining to prevent the r134a from attacking or penetrating them.

This was mentioned by one of our other members recently, I think it was MDchanic.

chip-powell

The hoses were the one thing that I did not replace. Mainly due to the cost, and that they appeared to still be in very good condition. I'm going to have to wait on replacing them for the time being (the money is already allocated elsewhere). I guess that I will recheck the O rings and then charge it up again to see if it will hold. Thanks for the advise guys.

VC455

In older cars, changes occur in the lining of the OEM hoses that create a film that is nearly equivalent in barrier property to the new hoses.

This should still be considered a possibility--just not the number one factor.

chip-powell

When you say "older cars", how old do you mean? 50s, 60's? This is a '71 cutlass.

Olds64

I've heard the same thing in reference to hardening valve seats in the head. I don't mean to call BS though.

In any event, when retrofitting AC to r134a, r12a or any other refrigerant it's best to replace the receiver / drier along with the hoses and orifice tube. I understand that MAWs can get carried away.

When I charged the AC in my truck yesterday I did it with the intent of getting by as cheaply as possible. So, I just added refrigerant without replacing parts or pulling a vacuum on the system. I've gotten away with it so far.

oldcutlass

If mechanic needed to ad freon, you have a leak.

Junkman

If your system still has refrigerant in it, but not enough to cool, then you can get away with adding refrigerant, since it hasn't been open to the atmosphere. I have done this many times in the past.


As for where did his refrigerant go, my best guess is that it escaped through the hoses. I have heard that many times, the refrigerant and oil will cause a barrier to be established in the hoses, but I have never seen it happen with any car that I have worked on. R12 is a larger molecule than R134A. I am in the process of converting the hoses on my 1962 Chevrolet to all barrier hoses, since the originals have become so brittle, that the clamps will no longer hold the refrigerant in. I also have heard from others that you can't do this, because the hoses will not go over the barb fittings. I used refrigerant oil and my heat gun, and had no problem pushing them on, on the ones that I have done so far. I had to stop, since to get the evaporator out of the cowl, it requires the removal of the fender, bumper, and hood. Since I usually work alone, this presents a problem. I am also sitting on the fence deciding if I want to tackle the seals in the compressor, since it didn't leak, and worked perfectly prior to the refrigerant loss. It is always a toss up where to stop parts replacement, especially on a system that is pressure sensitive. Some "O" rings are easy to acquire, but there is one very small one, that I have yet to find a source for, unless I want to use butyl rubber. The problem with butyl rubber "O" rings today, is that they come from China, and the quality is questionable.

edzolz

You should always pull a vacuum on the system before recharging. I pull the vacuum and let the system sit over night to make sure there are no small leaks that will cause the system to lose charge. If the vacuum is at max and stays overnight, there is a better chance of there not being a leak.

Junkman

I agree with you 100% about pulling a vacuum and then I pressurize with nitrogen, so I know that it holds both ways. Sometimes as a matter of financial concerns, people don't have the luxury of doing it the best way, and only want to get through the season. If the system is totally empty, then there is a severe leak, if only a little amount, there is a better chance that the "leak" is through the hoses, and that is an expensive repair for most.
I have a local hydraulic hose shop that will remove original fittings when possible, and re swage them onto the new barrier hose. It doesn't look 100% original, but it sure makes it a lot easier then not being able to buy a replacement hose at all, because the fittings are so weirdly configured with bends.

Fun71

Didn't we go through this a while back?

Posts from 2015:
https://classicoldsmobile.com/forums...-not-r12a.html

Junkman

old age forgetfulness.. Decided that I should look this up for myself. Seems that every site that I visit with the help of Google, agree that R134 is a smaller molecule. You can click on the posts for the links and verify this information for each one that I posted. There is a lot of good information out there, and we all have to keep an open mind, and we can learn a lot from this information.


www.allchemi.com/eng/refregerants/description/mackfri-134a.html



https://griffiths.com/ac-system-help.../r134a-vs-r12/


http://www.acsource.net/acforum/view...php?f=1&t=8578
at the bottom of the page.