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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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Old 05-09-2019, 07:56 AM
franan franan is offline
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R12 to R134

My plan for the summer is to convert my 1992 325i from R12 to R134. Any tips? What do I need in order for a successful job? Do I have to change the expansion valve? I know I have to change the receiver as well. Let me know Thanks.
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Old 05-09-2019, 08:43 AM
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Originally Posted by franan View Post
My plan for the summer is to convert my 1992 325i from R12 to R134. Any tips? What do I need in order for a successful job? Do I have to change the expansion valve? I know I have to change the receiver as well. Let me know Thanks.
https://itstillruns.com/convert-r12-...m-6616048.html
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Old 05-09-2019, 09:52 AM
bluptgm3 bluptgm3 is offline
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Wow, they did not recommend changing anything. Is that an over simplification?


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Old 05-09-2019, 10:07 AM
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Wow, they did not recommend changing anything. Is that an over simplification?


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I dunno. R-12 is Dichlorodifluoromethane and It may be the case that any elastomer resistant to it is also resistant to 1,1,1,2-Tetrafluoroethane R-134a. They are pretty similar chemistries.

But note IMPORTANTLY that R-134a is also banned for its (((Global Warming Potential))) and is being replaced by 2,3,3,3-Tetrafluoropropene, HFO-1234yf, a hydrofluoroolefin (HFO) with the formula CH2=CFCF3. It is also designated R-1234yf.

When my refrigerant must be replaced then I will order R-1234yf.

Among all of these changes the AC oils have compatibility problems.
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Scepticism and Animal Faith (1923)
Scepticism is the chastity of the intellect, and it is shameful to surrender it too soon or to the first comer: there is nobility in preserving it coolly and proudly through long youth, until at last, in the ripeness of instinct and discretion, it can be safely exchanged for fidelity and happiness.
(The Works of George Santayana p. 65)

Eschew eristical argumentation. I am responsible for what I write, not for your understanding of it.
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Old 05-09-2019, 10:55 AM
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My plan for the summer is to convert my 1992 325i from R12 to R134. Any tips? What do I need in order for a successful job? Do I have to change the expansion valve? I know I have to change the receiver as well. Let me know Thanks.
Don't change to R134a. R134a does not work as well as R12 so in a system designed for R12 you are going to lose around 20% of AC capacity. Instead use R12a. R12a works just as well as R12 so your AC will blow just as cold as it does now. Also R12a has a global warming potential of 8 vs R12 at 7300 and R134a at 1200. You can get R12a online from a couple of places. Personally I use Frosty Cool. Somethings to keep in mind. R12 and R134a use different connectors on the AC system so you are going to want to either install R134a connectors or use adaptors. It takes less R12a to fill a system so you are going to want to do the math to figure out how much to use. Use a scale to measure the refrigerant. The system needs to be under a vacuum before you put refrigerant in because there should not be any air in it. Fix any leaks before you put new refrigerant in. If you are low on R12 you have a leak. If the system still has any R12 in it, take it to a shop to have the R12 removed. R12 is not something you want to dump into the air.
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Old 05-09-2019, 11:14 AM
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HC-12a A.K.A. R-12a EPA Unacceptable Substitute

"Substitute (Name Used in the Federal Register): All flammable refrigerants, including OZ-12 (Hydrocarbon Blend A), HC-12a (Hydrocarbon Blend B), and Duracool 12a except HFC-152a and HFO-1234yf in new MVACs.

End-uses: Motor vehicle air conditioning, retrofit and new.

Reason: Lack of adequate assessment that characterizes incremental flammability risk."

https://www.epa.gov/snap/unacceptabl...e-refrigerants
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Scepticism and Animal Faith (1923)
Scepticism is the chastity of the intellect, and it is shameful to surrender it too soon or to the first comer: there is nobility in preserving it coolly and proudly through long youth, until at last, in the ripeness of instinct and discretion, it can be safely exchanged for fidelity and happiness.
(The Works of George Santayana p. 65)

Eschew eristical argumentation. I am responsible for what I write, not for your understanding of it.

Last edited by Doug Huffman; 05-09-2019 at 01:02 PM.
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Old 05-09-2019, 11:38 AM
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It is only against the EPA to use R12a in a R12 system directly. Using R12a in a R134a system is fine by the EPA and so is using R12a in a R12 system after it has been converted to R134a. Converting R12 to R134a just involves changing to R134a fittings and putting R134a in. Considering there is no way of know if R134a was in the system after you put R12a in, I would say that just swapping the fittings is fine. If you want to be 100% by the books you could put R134a in the system and then recover it, but that seems silly to me.
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//1992 Mazda Miata - cat delete, power windows, oil filter relocation


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