The Org - Serving W116 Enthusiasts since 2004!

Main Menu

which way to go?.....Air conditioning R12 to R134a

Started by BMA, 26 May 2024, 01:40 AM


Hi Guys, I am very confused which way to go to convert my empty R12 system to R134a?
System is empty for many years.
Replacement refrigerant R 413a is hardly available anymore here in Germany, so R134a seems the way to go.
(Of curse the first test will be to put overpressure into the system to check if its leakproof.)

Some change almost everything, including a new compressor which works with R134a (or put new O-rings into the compressor), other expansion valve, all gaskets and what so ever, .....probably even new tyres :-)...... Other just changed the dryer, pressure switch and some gaskets and did NOT change the oil!....So just added some PAG oil. That's the way I planned as well but I read Nightmare stories that the old R12 organic oil does not work with the R134a (PAG Esther) oil. I have a Delco compressor, model no.1131236 in my 1979 6.9 (manual climate system, no automatic AC).

Would be happy about getting the ultimate efficient advice from people with experience in that field which way to go?

Many Thanks in advance,


PS: That I need also the R134a fill in adaptors is clear.
happy having finally a 6.9 # 7271 in my garage, nice to cruise!


I am also interested in this thread, as I'm almost at the point where the A/C system can be put in operation again.

I am looking into R437a, which should work as a drop-in solution for R12. It works with the mineral oil, and the cooling capacity should be the same or even better than R12 (statement from a Klimaservice, so take it with a grain of salt).

Not sure where in Germany you are located, but it seem this company works with R347a : . Maybe they could also give you some tips?
1971 R107 350 SL
1972 W108 280 SEL 3.5
1975 W116 280 S
1975 W116 450 SEL 6.9 #140
1977 W123 230
1992 W124 230 CE
2001 Ducati Monster S4


Many Thanks Max-NL,
Kühler-Diek in Hamburg is just 200 km distance. Will call them tomorrow.

My level of knowledge meanwhile is in order to let remain the work and expenses in a moderate level:

1. Drain oil of the compressor when installed
2. perhaps loosen a little to turn so that the oil runs out well
3. some O-rings change to green ones, if 2. to do
4. pressure test of the whole system with a special gas.
5. let fill into the system 285 ml PAG 100 for the compressor  plus maybe some ml more for the exchanged dryer. My compressor model is the Delco/ Harrison A6 mo. nr. 1131236
6. maybe flushing the system
7. evacuation
8. 134a filling in: 850 Gramm. (R12 was 1000 Gramm, factor 0.85 when go to R134a)
9. Hoping it will get cold and system is not leaking a week later! :-)

happy having finally a 6.9 # 7271 in my garage, nice to cruise!


Probably not what you want to hear, but I wouldn't bother with the Delco compressor. Even if you're able to get it working again after a drain / refill + new o-rings, they're not particularly efficient or reliable. I invested time and money into getting mine working only to have it fail completely a couple of months later.

Almost a year after posting this, my AC is still blowing ice cold (used it yesterday!):


I am living in Germany, so unless climate change pretty moderate climate.
What you did is admirable, but exactly what I wanna avoid!

If my compressor breaks down, as you are promising, I can always buy another one, but maybe it will last?...So why do something preventively that might not be necessary?

Regards from currently sunny Germany,

happy having finally a 6.9 # 7271 in my garage, nice to cruise!


I have converted 2 w116 to r134a with the manual AC, both were behaving similar , on my 6.9 i replaced all seals in the compressor and also the dryer and expansion valve.
Perfomance is ok for germany i would say but don't expect any good cooling if it gets far above 30c , what i find weird that if you start driving the car it cools very good but on long drives it the aircon gets weaker especially if you use it on a high setting.
My w126 with r134a cools much much better.


I found a tank of R-12 locally which I am hoping to fill mine with (after a leak test of course). It took a while but they do exist if you are willing to wait on a used item classifieds.


I would say that will be impossible in europe
As far as i know even when R12 was available it was never sold in cans in europe especially in germany were very few cars and aircondition and nobody would try to fill it up himself because it mostly were only luxury cars that had aircondition.


Would like to finalise this post and note that our world can be so small!

After posting that thread here as a German in a mostly US Portal, Ramiro, see above, gave me some hints. Then we found out that he lives 70 km (45 miles) next to me in Germany!  :)

....So due to him my problem is fixed! In his impressive garage we did this "cool job".  Thank you a lot Ramiro!

What did we do? As he told me to test, if I have maybe still some pressure on the system, we just added a replacement into the system, because I had pretty much pressure in the system! Without removing the compressor and draining the oil and filling up with R134a compatible PAG Oil. Compressor removing shall not be an easy job in a 6.9 btw! My brand new bought dryer and sealing remain in my garage. We just added replacement refigiant and now: It's cold and yes, even pretty cold if I want it to be very cold! :-).....So now, after 3 days driving, it still works, ....cross the fingers , many days more!  Best Regards, Björn
happy having finally a 6.9 # 7271 in my garage, nice to cruise!


Fabulous news, and great story!! Well done Mr. Ramiro