Quick background...

Bought car in the winter, a/c didn't work, PO converted to R134, didn't care then, it's about to get VERY hot in AZ, I care now, trying to fix, read below...

No pressure on the low side, I hook up venturi style vacuum pump and manifold to see if there is a leak before I attempt to start replacing everything. My air compressor is kind of lame and I can only get about 19" vacuum on the system however it has been holding that for 4 hours now without a loss. Am I safe in assuming that I don't have a leak? I know you need to pull 29" for hours in order to boil off the water before refilling, but at this point I'm just checking the mechanics.

I also know I'll need to get a new dryer and might as well replace the expansion valve but I'd like to not have to replace the compressor or track down mystery leaks once I do recharge.

It depends on the compressor. The front seal likes to leak, especially on the R-4 design.

Look for oil/dirt residue on all the connections. I ended up buying a new compressor last year. The rebuilt just lasted a week past it's one year warranty. Get a Hodyon (Hancock Industries) compressor. If you are going w/R134 again, get the thick GM specified oil or BG Fridgiquiet.

Holding vacuum is different than holding pressure, so no guarantees. Plus you need to use a good pump to get to 29" IIRC, anything less then 24" does not extract all the moisture.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

Well, I don't have any experience with my Mercedes...but with my Toyota, I know that it would only pull about 24" vac...I refilled with R-134, and it lasts about a year and a half before I notice that its not working quite as well as it should and it needs a recharge...

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

On the subject of background, what is the year/model of the car in question?

No. The typical operating pressure exceeds that pressure differential by a factor of 30.

Need more info. If PO had converted, how long ago and did the items listed above get replaced then? Trying to figure out why you assume the drier and expansion valve need to be replaced. Is there any pressure on high side? Is there any refrig in system currently? Have you tried to fill system if the above answers are no? You can purchase or rent a leak detector real cheap, fill the system and check for leaks. Lots of options before just tearing into system and replacing parts just because you think they are bad.

Also FWIW I have done countless A/C systems and have never pulled more than 19 - 21in vac on any system including my own 134A conversion 7 years ago and blow low 30's out of vents in mid summer.

Only what was left after pulling 19" of vacuum!!!!!!!

Even a moisture-laden system can work for a while.

Sorry... 82 300D, I don't know when the parts were converted and there is 0 pressure on the low side or high side. So I do need a new dryer no matter what as i'm sure it's saturated by now. I've got so much grime on my compressor from my leaky oil cooler lines I can't tell if it's got that tell tale oil "dusting" around the seals. So how's the luck with the rebuilt R4 compressors? Worth a try or do they always take a dump in short time?

It has been my experience that the older R4 compressors work fine on R12 or ES 12, but the higher pressures associated with R134 will shorten it's life somewhat! I did a successful conversion, but I went with Envirosafe Refrigerant and it makes a world of difference! Envirosafe is not poisonous like R134 and it requires a lot less of it and it works best next to R12. It also operates at much lower pressures and it is compatible with all compressor oils, but oil for an R12 system is still easy to get and works better. I live here in Apache Junction AZ and i drive in the summer with no problems. Envirosafe or ES 12 because it does operate at much lower pressures, your fuel economy improves dramatically and your acceleration improves greatly with the system at maximum too! I'll find the link to envirosafe and post it here in a minute or two. It has to be odered over the internet, it's not available locally, but it is worth it since we have a little time before the heat get's fierce!

http://www.es-refrigerants.com
http://www.duracool.com

Duracool is another hydrocarbon based non-toxic refrigerant that works well in these systems too and there are dealers close to Arizona as well. Envirosafe will arrive quickly with a credit card and it is also a little cheaper by the case too.

One thing you really need to watch out for! Moisture in an R134 system will corrode the hell out of metal parts!!

If I change to ES12 or Duracool, will I be able to find an auto ac shop who will vacuum out my system before I put in the new gas? I thought that most shops will not want to contaminate their vacuum machines.

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

Apache Junction ehh? I'm at Sossaman and University, we're practically neighbors! Anyway I was able to tweak my air compressor up to get a full 28" (i know, 29-30 is recommended) and it held for 4 hours without a hint of vacuum loss. I also "jumped" the compressor clutch to make sure it wasn't seized, it activates quietly. So I decided to just roll the dice and charge it with some cheap R134 and see how long it lasts.

I added one 14oz can with oil, stop leak, dye and refrigerant and another 12oz can of just refrigerant. That brought me up to 25psi low side and 200psi high side with ambient temps right at 70 degrees. From the moderate amount of research i've done, the system should take 35 psi low side while the high side shouldn't be any higher than 175 psi at 70 degrees. I was afraid to add anymore with fear of a burst on the high side. When I shut everything down and disconnected the hoses I noticed some minor bubbling inside the low side port and I held my finger over the port and could feel a bit of pressure pushing back. I might be in luck and only have a bad shrader (spelling?) valve, I reinstalled the cap very tightly but I'm sure that will need to be addressed...

However, it blows ICE cold, in fact I stuck my finger in the vent (haha) and I couldn't keep it there for anymore than a few seconds without it getting uncomfortably cold. I know once the ambient temps start to rise my efficiency will drop dramatically, but this is just a test to see how long it'll hold pressure. Come summer time, if I need to add a can every month that would be cheap and not the end of the world. Anyway, thats my story so far.

Anyone know what pressures I should see on my manifold with R134 and 70 degree ambient temp?

FWIW, this is an interesting article on the use of Hydrocarbon Refrigerants in autos:

http://www.theautochannel.com/news/2005/04/25/047878.html

I not only find this interestingly perjorative to anything other than R134A, but also full of crap!

R12 when exposed to air and heat will turn into deadly phosgene gas which kills without warning. At least you get to smell it first and get away since it smells like smelling salts.

R134A will turn into deadly and poisonous gas causing instant narcossis and death when it bursts into flame. R134A has no warning smell and comes on like Carbon Monoxide and puts you to sleep before it kills all your brain cells! Since R134A has to be charged into the system at higher pressures than R12 and requires 10% MORE I hardly call this risk free. This article has no real facts to back up this position and no sources of information you can fact check! Envirosafe meets all these requirements and the MSDS (Material Safety Data Sheet) proves this is one of the best to use and is 79% safer than R134A!

I have never used Duracool myself since Envirosafe has served me well and is very user friendly. Oh, by the way, I tried to get Envirosafe to burn and I had to discharge it into an open blow torch burning MAPP gas at full throttle and even then the flame is not easily ignited!

I would love to see who the article sponsors are! All those who support this "public service announcement" are heavily invested directly in the DuPont manufacturing family and hold stock in this particular genre.

They all keep getting paid when we buy R134A whether it works in our Mercedes Benz's or not! Notice Mercedes Benz isn't in the list of supporters?

I thought the interesting part was that it's not legal in 19 states, so someone has a problem with it. As I said, I simply wouldn't bother unless R-12 started getting really expensive. At current prices, it's just more trouble than it's worth to play with "alternatives" and R-134a just doesn't perform well enough in the old R-12 systems.

What I find interesting here is that in Arizona, R12 isn't made available for mobile AC systems though. If you can get R12 for your older vehicle, it's not legal either!

What we can get is Freeze 12 which is basically R22 and propane which is highly combustible and inflammable! Freeze 12 causes permanent nervous system damage and has even been associated with Alzheimers disease! If it goes up in flames, you will not likely escape without serious injury with Freeze 12 upon explosion.

I find it hard to believe it is illegal here since I had my container of Envirosafe sent to my workplace at Penske and it was clearly marked as to what is was and no one said a thing! This was the size of a 5 gallon propane tank!

I would be more inclined to believe that funds exchanged hands here to make sure that "Coke" got the lions share of the market, in this case Coke being R134A.

I would like to know what statute law is being broken with Envirosafe being used and the article should have cited references instead of being so vague.

AFAIK, R-12 is legal everyplace in the U.S., with the required license. I simply ask my indy to charge my system with R-12 and he does (hopefully following all the rules required by his license). If you look on eBay, more than a few vendors sell R-12 and require a license for purchase. That does not mean that every shop will choose to sell R-12. Unless there is a specific state law in AZ, you should be able to buy it someplace there as well.

It is interesting that you are able to obtain HC based refrigerant in AZ. Are you able to purchase it for auto use, or do you have to charge your own system? You might want to check on it's legality just to protect yourself from any potential liability if you are buying it from a supplier on a "don't ask, don't tell" basis.

This article specifically says, "In the United States, it is illegal to use hydrocarbon refrigerants to replace CFC-12 used in cars manufactured before 1994." It sounds like the legality of it's use in later cars is a little fuzzy. However, this does not give a legal reference either:

http://www.sae.org/news/releases/05hydrocarbon.htm

I also would not play with freeze 12 or any other blends.