R12 to R134 conversion question

[Mr. BILL]

I was talking to a Indi the other day who only works on BMW's. He said it IS OK, to convert from R12 to R134 by just changing from one to the other. This is contrary to what I've been lead to believe.

Is this guy correct? He's pretty much a BMW guru.

[Tiger]

Yes, he is correct.

[ocampg]

go with freeze 12, can be substituted directly for r-12. Though its not stated, it can actually be mixed with r-12 too.

[Mr Project]

In the case of my 535i, the compressor was compatible with R134, so I was able to:

Remove and flush every component (except compressor, no flushing)
Carefully dry every component
Drain oil from compressor
Re-assemble system with new R134-compatible o-rings & nylog lube & POE (NOT PAG!) oil.
Evacuate, evacuate, evacuate.
Recharge system with R134.

So far it's been a couple months and I still have vent temps in the 40s with over 80 degree inlet temps. The problem with just draining the R12 and filling with R134 is that the PAG oils supplied with many R134 kits do NOT play well with R12. Eventually they will cause problems.

[ryan roopnarine]

are you saying that everything's ok without you changing the drier?


In the case of my 535i, the compressor was compatible with R134, so I was able to:

Remove and flush every component (except compressor, no flushing)
Carefully dry every component
Drain oil from compressor
Re-assemble system with new R134-compatible o-rings & nylog lube & POE (NOT PAG!) oil.
Evacuate, evacuate, evacuate.
Recharge system with R134.

So far it's been a couple months and I still have vent temps in the 40s with over 80 degree inlet temps. The problem with just draining the R12 and filling with R134 is that the PAG oils supplied with many R134 kits do NOT play well with R12. Eventually they will cause problems.

[Mr Project]

OOPS!! Thanks for reminding me!! Yes, I did change the drier, which is another thing that really must be done when converting.

[Tiger]

PAG oil is NOT compatible with R12 oil... but if you go with those that has Polyol Ester then it will work with mineral oil you got in the system...

[MicahO]

I swapped my van to Freeze 12 about a year and a half ago, had the R12 evac-ed, loaded the Freeze-12 myself (at 75% of the R-12 capacity), and it's run nice and cold since then. Still have a half-case of the stuff.....

[ocampg]

I swapped my van to Freeze 12 about a year and a half ago, had the R12 evac-ed, loaded the Freeze-12 myself (at 75% of the R-12 capacity), and it's run nice and cold since then. Still have a half-case of the stuff.....

right, I've read you dont really have to evac the old r-12, but it is recommended for environmental reasons, so that if another shop were to have to evacuate the system, it would be pure which can be recycled/reused rather than a mix.

[Bill R.]

old r12 but the manufacturer states that the r12 and freeze 12 are compatible with each other and will work fine





right, I've read you dont really have to evac the old r-12, but it is recommended for environmental reasons, so that if another shop were to have to evacuate the system, it would be pure which can be recycled/reused rather than a mix.

[MicahO]

It's also tough to tell how much is actually in a system, and since you don't want to overfill it, the best baseline is an empty system, plus 75-80% of the R-12 recommended capacity.

I was quite concerned about the overfill possibilities, and decided to take the safest route. It also happened to be the legal way to go.


old r12 but the manufacturer states that the r12 and freeze 12 are compatible with each other and will work fine