AUTO HVAC - R-12 TO 134A - I Need Correct Proccedure

Your mechanic is right. You must convert away from R-12. You will need to change the pipe fittings on the supply lines to the new style. There are no issues with the change over. Please make the conversion.

Thank you for your response, other than adapting to new fittings, is any special PAG oil additive or make up oil required? I just want to make certain that as I do this going forward that the mechanic does not short cut any part of the process. The process call out or mini SOW is kind of what I was looking for, any guidance?

Thank you once again. Mike

The oil requirements for the R12 to 134A auto refrigerant conversion can be found at the Dupont website.

Specifications found here require that "at least 95% of the mineral oil or alkylbenzene be replaced with POE (polyol ester) of similar viscosity requiring multiple oil changes".

I also saw elsewhere where all a/c hoses older than 12 years should be replaced.

The filter dryer should be replaced.

The compressor seals should be replaced.

It may be necessary to flush the system. This was originally recommended by SAE (Society of Automotive Engineers) who developed specifications, but they have backed away from this as a strict standard somewhat.

The condenser may be damaged from rocks and is more likely to leak than the evaporator.

I hope this helps. Good luck.

Thanks I appreciate your helpful detail. I will proceed accordingly and get back to you.

You might not want to go that way at all. R134 numbers are not as cold.

Consider this post.

Freeze-12

Hi there,
Most all the R-12 substitues are a blend of butane and propane, in a percentage to produce approximately the same cooling effect as R-12. They work fine as long as there's no leak in the system. They are compatible with both mineral and PAG oils. (I don't have personal experience with the PAG oils, however, just repeating what I've read.) They are actually more efficient at cooling than R-12 is.
The problem is that the system MUST be labled that there is an R-12 substitute in the system. Failure to do so is against the law! Also, if there is a leak in the system, (and there almost ALWAYS is,) the percentage of butane and propane will change, and then the system won't work as designed after awhile when one of the gasses leaks out in a greater percentage than the other.
Interestingly enough, these gasses are used in many countries around the world instead of R-12, completely legally. They are environmentally friendly, even when leaked into the atmosphere. There is a slight danger of fire if they leak into the engine compartment in a large volume, but no worse than a can of hair spray.
If one uses them be aware that the liquid volume of these gasses is much different than R-12 - it takes much less to fill the system. If I remember correctly, it's on the order of 1/3 the quantity by weight.
Don't try to mix butane and propane to approximate the same thing, as the substitutes like Freeze-12 have been filtered and more water has been removed from the gases. Using regular butane and propane may rust out the AC system from the inside out.
I am personally aware of a Jag that has been using this stuff for 7 yrs now with no ill effects...

I'm sure that others will have plenty to comment on regarding this subject.

Regards. __________________
Richard Wooldridge
'82 300D 4.3L V6/T700R4 conversion

If you are not mindfull when doing a refrigerant swap, the result is usually wasted money and time (in my experience anyway).

Some things you have to keep in mind when changing over to a different refrigerant:

1) Oil: R12 uses mineral oil, and this oil is not miscible with R134a. If R12 oil is used with an R134a refrigerant, the compressor will not last very long. The oil will be carried out of the compressor during operation and will not be returned through the suction line to provide the required lubrication. Critical.

2) O-rings and compressor seals: need to be changed to ensure that the seals are compatible with the new refrigerant and oil.

3) Filter/drier: must be changed because it will contain oil and moisture from the previous system and the dessicant material may not be compatible with the new refrigerant and refrigerant oil (its good practice to change the filter driers whenever you open an old system).

4) Expansion valve: using a different refrigerant will result in a change in the evaporator superheat that the system was originally designed for.

5) System flush: all of the previous oil must be removed so as to not contaminate the new oil and refrigerant.

6) Leaks: before attempting any work on the system, ensure that there are no leaks in the system (system should hold a vacuum in the 200 micron range)

Good luck.

Thank you for this good insight. My goal is to do this properly and I feel now I have some solid footing in order to proceed. Q. as a general rule will one have to go with the OEM dryer or are there acceptable after market units since ultimately someone in the Auto supplier community is making this for the OEM anyway? Please advise. Thanks again for the helpful insight.

Generally you can use any filter/drier that is designed for the refrigerant and the capacity of the system. You just have to be mindfull of connections. You have to ensure that the filter/drier can connect to the existing hoses.

Good luck.

There are two things you should do.

1) convert from R-12 to R-134a because not only is R-12 MUCH more expensive now, it will be totally unavailable in the fairly near future.

2) find a different mechanic. You cannot simply replace the R-12 with a different Freon®, the compressor will need to either be changed or retrofitted, the lube oil in the system will have to be flushed and replaced, and only a certified technician can open the system to do any of this. Based on your guy's comments, I doubt he is a certified refrigeration technician.

Please report back on your SUCCESS! (What's the car?)