Thread: A/C 134 conversion ???

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I am trying to get the a/c working in a '76 Monte Carlo. The compressor is working, I bought a kit to convert it to 134, filled it up, and it worked. I even patted myself on the back a little because everything went as planned on the first try..................until the next day when I realized that the refrigerant had leaked out. Now for round two, the hoses look to be in good condition, and I am going to replace all of the o-rings. What other parts should be replaced while I am at it?

Did you replace the dryer? I am getting my streetrod's R12 system converted this year and have been told that if the hoses are okay, then the only thing I would need to replace would be the dryer. Although replacing the condensor might be beneficial due to the differences between the two systems, I have been told that it is not a necessity to replace. Mine needs new seals anyway so they will all have to be replaced.

The only other car that I have converted was a 91 Taurus which was several years ago. The first attempt only lasted about 2 days. On the second attempt they replaced the seals, and everything was good for about 3 months and then it failed again. That Taurus a/c was always problematic.

Nope, I didn't replace the dryer. That is the kind of info I am looking for. I don't know what else is required, or recommended. I converted my sons car several months ago, just replaced fittings and re-filled. It has been working great so far. Maybe I got lucky on that one.

Everything I have read, does not mention the need to replace components.

Lots of reports like these on google:
http://www.teamchicago.com/imperial/imp-ac.htm

Here is what the EPA says:

How Much to Charge into the System
The amount of R-134a charged into the system should normally be 80-90% of the amount of R-12 in the system. Most a/c system manufacturers provide guidelines regarding the amount of R-134a to be used.

Lubricants
PAGs vs. Esters
The mineral oil used with R-12 cannot be sufficiently transported throughout the a/c system by R-134a. Automobile manufacturers tested both PAGs and esters for refrigerant/lubricant miscibility, lubricity, chemical stability and materials compatibility. In the process of developing recommendations, they also considered the additives and conditioners present in the oils. Most - but not all - chose to use PAG lubricants in new vehicles equipped with R-134a, and are also recommending PAG lubricants for retrofits. Some compressor manufacturers are shipping new compressors with PAGs, some with esters, and some are shipping them empty.

PAGs are hygroscopic, which means that they will draw water from the atmosphere when exposed. Many aftermarket a/c specialists are choosing to use ester lubricants because they believe that the hygroscopic characteristics of PAGs may limit their lubricating ability and introduce corrosion into an a/c system. Esters are also hygroscopic (although less so than PAGs), and care must still be taken to ensure that excess moisture does not go into the system.

It is good practice to use PVC-coated gloves (or, if that is impractical, barrier creams) and safety goggles when handling these lubricants, since prolonged skin contact and/or even brief eye contact can cause irritations such as stinging and burning sensations. You should also avoid breathing any vapors produced by the lubricants, and make sure to use them in well ventilated areas. And be sure to keep both PAGs and esters in tightly sealed containers, both so that humidity does not contaminate the oil, and so that vapors do not escape.

Flushing
The amount of mineral oil that can safely remain in a system after retrofitting, without affecting performance, is still being debated. It was originally thought that any mineral oil left in the system might cause system failure. As long as the tech has removed as much of the old mineral oil as possible, any residual R-12 left in the system should not have a significant effect on the performance of the system. Removing the mineral oil may require draining certain components. Unless the vehicle manufacturer recommends flushing the system during the retrofit procedure, a service tech can assume that flushing is not necessary. (Although the SAE J1661 procedure for retrofit includes flushing, SAE no longer believes that flushing is critical to a successful retrofit.)

Hoses and O-Rings
When R-134a was first introduced, it was thought that all non-barrier/nitrile hoses would have to be replaced during an a/c retrofit. Early laboratory tests showed that the small R-134a molecules leaked through the walls of non-barrier hoses more readily than the larger R-12 molecules did. In the lab, this caused unacceptably high leakage rates. More recent testing, however, has shown that oil used in automotive a/c systems is absorbed into the hose to create a natural barrier to R-134a permeation. In most cases, the R-12 system hoses will perform well, provided they are in good condition. Cracked or damaged hoses should always be replaced with barrier hoses.

Unless a fitting has been disturbed during the retrofit process, replacement should not be necessary. Most retrofit instructions call for lubricating replaced O-rings with mineral oil to provide this protection.

Compressors
Industry experts once thought that a retrofit would require compressor replacement. This belief helped create some of the horror stories about the expense of retrofitting. Now it is routinely accepted that most compressors that are functioning well in R-12 systems will continue to function after the systems have been retrofitted.

When a compressor is first run with R-12, a thin film of metal chloride forms on bearing surfaces and acts as an excellent anti-wear agent. This film continues to protect after the system has been converted to R-134a. This helps explain why a new R-12 compressor may fail more quickly if it is installed in an R-134a system without the benefit of a break-in period on R-12.

A few older compressors use seals that are not compatible with either R-134a or the new lubricants. The compressor manufacturer can identify which compressors need special attention. Any compressor that has seals made of Viton® should not be used with R-134a because the refrigerant will cause the seals to swell excessively.

Of course, any compressor that is not in good shape should be replaced during the retrofit procedure. Service techs should make sure that any replacement compressor is approved for R-134a by its supplier.

Desiccants, Accumulators, Receiver/Driers
R-12 systems use an XH-5 desiccant, while R-134a systems use either XH-7 or XH-9 desiccant. Some manufacturers recommend routine replacement of the accumulator or receiver-drier to one containing XH-7 or XH-9 during the retrofit procedure. (Any systems with silica gel should also be switched to XH-7 or -9 desiccant.) Others recommend leaving it alone. Manufacturers generally agree, however, that the accumulator or receiver-drier should be replaced if the vehicle has over 70,000 miles or is older than five years, and is opened up for major repair. In that case, the only recommendation is to use the R-134a-compatible desiccants.

Condensers and Pressure Cutout Switches
When retrofits were first studied several years ago, it was thought that the condenser and perhaps the evaporator would have to be replaced to maintain an acceptable level of cooling performance on a retro-fitted system. Now, it is generally accepted that if an R-12 system is operating within the manufacturer's specifications, there may be no need to replace either part.

It is true, however, that the higher vapor pressures associated with R-134a may result in lost condenser capacity. When retrofitting, service techs should consider how the air flow and condenser design on the particular vehicle will affect the success of the retrofit. In some cases, the installation of pusher-type engine/condenser cooling fans mounted in front of the condenser have improved the performance of retrofitted a/c systems.

Service techs should also be aware that bent, misshapen or improperly positioned airflow dams and directors may affect performance. Some OEMs are including hood seal kits as part of their recommended retrofit procedures. In addition, systems that are not equipped with a high-pressure cutout switch should have one installed to prevent damage to a/c parts and to prevent refrigerant emissions. The installation of a high-pressure cutout switch will shut off the compressor when high pressures are encountered, reducing the possibility of venting the refrigerant and overheating the engine cooling system.

Refrigerant Controls
Refrigerant controls -- whether they are orifice tubes or expansion valves that meter refrigerant flow, or pressure cycling switches or other pressure controls designed to protect against freezing -- may have to be changed during the course of a retrofit.

The kit I used said to evacuate the system completly and install a new reciever/dryer and included a cartridge that allows the seals to accept the 134.Worked with no issues.