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W126 1985 280SE RHD - R107 1986 420SL RHD
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Discussion Starter #1
Hello all,

I will be reconverting my 126 from R134 back to R12. I purchased 20kilos of R12 however prior to flushing and replacing filters and expansion valves, is there a way to check that the contents of the cylinder are 100% R12?

Can an A/C mechanic attach gauges on the cylinders and through the reading assess whether the contents are 100% R12?

Additionally, I replaced the original compressor with a sanden R134 compressor which I am told is slightly smaller (one less piston). If I change the oil in this compressor to mineral oil, will it still be ok to use this R134 compressor with R12?

The cost of a new original compressor is USD 1600 which is a bit too much!

Right now the readings I get at the center vents are 66 degrees fahrenheit in the shade (59 on a good day for some reason). R12 should be giving me about 42 degrees fahrenheit and perhaps 50 at stop and go traffic if I am not wrong??

Temperatures reach 40 degrees celsius (104 fahrenheit) and the a/c does ok-ish if I have parked in the shade otherwise it is a sauna! And the longer I use the a/c during the day the less cold air I get.

I would really appreciate any advice someone may give me as I am not sure if the guy I bought the R12 from gave me a 100% R12 or a mixture

Thanks for any advise in advance
 

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1995 E320 (totalled) 91 420SEL W126 (retired) 2002 S500 W220(retired); 2008 C300 Sport W204
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662 Posts
You cannot tell which freon is in a system except by keeping the labels on the car up to date.
Sounds like you may have a leak in the system. Did the R134 conversion work well when it was first installed? If it did maybe it needs a little boost of Freon.

R12 does work better that R134. Not sure about the compressor. I know that you can use less R12 than 134 so it will probably work ok. (lower pressure needed) Most "R12" available is a hybrid like Freeze12. I use Freeze 12 in my 91 420SEL with orginal compressor and system and it works great. I live in the Phoenix AZ area so we are always over 105 degrees F in the summer months. My car interior is a comfortable 68 degrees F. THis replacement uses standard mineral oil and uses about 10% less than original R12 would use.
 

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W126 1985 280SE RHD - R107 1986 420SL RHD
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161 Posts
Discussion Starter #3
You cannot tell which freon is in a system except by keeping the labels on the car up to date.
Sounds like you may have a leak in the system. Did the R134 conversion work well when it was first installed? If it did maybe it needs a little boost of Freon.

R12 does work better that R134. Not sure about the compressor. I know that you can use less R12 than 134 so it will probably work ok. (lower pressure needed) Most "R12" available is a hybrid like Freeze12. I use Freeze 12 in my 91 420SEL with orginal compressor and system and it works great. I live in the Phoenix AZ area so we are always over 105 degrees F in the summer months. My car interior is a comfortable 68 degrees F. THis replacement uses standard mineral oil and uses about 10% less than original R12 would use.
Thanks for your reply. I have had R134 for a few years now. The conversion was done in 2008. It is ok during the summer months. The lowest I can get out of the vents is 66 degrees F and is only comfortable if I parked in the shade otherwise it takes 10 minutes to get going.

I was told that I should get readings of 45 degrees F and R12 will help achieve that and will cool faster.

I found some R12 (supplier claims it is old stock dupont) and my question was more along the lines of whether there is a way to actually test the freon contents in the cylinder I purchased to ensure the freon is 100% R12 before I go about flushing and replacing parts. I only have the supplier's word that it is R12. If I flush, replace parts and oil and then charge the system and find out it is not R12 in the cylinder, then the work is pointless.

I assumed there is a way to attach gauges to the cylinder and via the pressure readings, understand whether it is R12 or some other freon?
 

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1974 450 SEL Champagne Beige Metallic(Sold); 1986 560 SEL Champagne Metallic
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Is the R-12 you received in the small cans, or did you get one large cylinder with a valve already attached? If it is the large cylinder, then you have no way to prove that it is pure, clean R-12 as various freons mix easily and the standing pressure is not a sure indicator of purity. Do you have a good reason to suspect your supplier? Here in the US it is illegal (also dangerous) to reuse or introduce gas into a freon container; that is what a recovery cylinder is designed for. If you have the small cans, then you are safe as once pierced they cannot be refilled or reused. Make sure and install a new filter-drier in the system replacing the existing one in front next to the radiator fans, as this is where all internal contaminants end up trapped. Pull a deep vacuum to remove all moisture before introducing the new refrigerant, R-12 is sensitive to moisture. Good Luck on your re-conversion! Cheers, Ron
 

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W126 1985 280SE RHD - R107 1986 420SL RHD
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161 Posts
Discussion Starter #5 (Edited)
Is the R-12 you received in the small cans, or did you get one large cylinder with a valve already attached? If it is the large cylinder, then you have no way to prove that it is pure, clean R-12 as various freons mix easily and the standing pressure is not a sure indicator of purity. Do you have a good reason to suspect your supplier? Here in the US it is illegal (also dangerous) to reuse or introduce gas into a freon container; that is what a recovery cylinder is designed for. If you have the small cans, then you are safe as once pierced they cannot be refilled or reused. Make sure and install a new filter-drier in the system replacing the existing one in front next to the radiator fans, as this is where all internal contaminants end up trapped. Pull a deep vacuum to remove all moisture before introducing the new refrigerant, R-12 is sensitive to moisture. Good Luck on your re-conversion! Cheers, Ron
Thanks for your reply Ron.

I got the R12 in 2 large cylinders of 10kilos each. The supplier (I only had contact with him once and that was when I went to pick up the cylinders) said he has a large cylinder (I believe it was 500 kilos) and re-filled the 10kilo cylinders I picked up with Dupont R12. They have a valve attached on them. The 2 cylinders I got have "R12 refrigerant" written on them with various faded guidelines but they are clearly old cylinders (as he said old stock) and he told me he simply re-filled them from the larger Dupont one from another location which I could not verify. I saw other empty "R12" cylinders lying around which he said he would be filling up.

It seems I will have to run the risk of doing all this work without knowing for sure what's inside these 2 cylinders.

Since he refilled the cylinders, does this mean the quality of the freon will be lower? (if it is actually R12 that I got)
 

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1995 E320 (totalled) 91 420SEL W126 (retired) 2002 S500 W220(retired); 2008 C300 Sport W204
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There is really no way to know if it is pure R12. If he refilled the cylinder(s). There may even be moisture contamination. If you can buy an R12 replacement (not R134) in smaller sealed cans then you can be sure that is it not contaminated.

I still think you can get more chill out of the system you have now. If the system is fully charged you should be getting about 45 degrees F out the center vents with R134. On a low humidity day (10% humidity) you can acheive as low as 35 degrees F with R12.
 

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560SEC 1989 Smoked Silver ,Burgundy Interior
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compressors are 200 dollars nippon denso original remanufactured on ebay going back to r12 your crazy mine is Ice cold with r134 cause I did all the upgrades the right way
 

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2012 CL550 4MATIC Coupe
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compressors are 200 dollars nippon denso original remanufactured on ebay going back to r12 your crazy mine is Ice cold with r134 cause I did all the upgrades the right way
+1

My r134 conversion blows ice cold too. Mapearso was in my car with the air on and remarked that it was actually blowing icicles. So the "It doesn't blow cold enough" is a myth.

The 'right' way is to remove ALL of the old seals in the system and replace them with r134 grade seals. The compressor needs to be converted too. You also replace the valves as well.
 

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W126 1985 280SE RHD - R107 1986 420SL RHD
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161 Posts
Discussion Starter #10 (Edited)
A technician here has contacts with a company which has a refrigerant analyser, so to speak, and can detect the freon contents so I am waiting to hear what he has to say about it.

I actually have two 126s both on R134. The SE got a new compressor whereas the SEL still has the original compressor and a slightly larger condenser as it was purchased originally in the Gulf. The 126's supplied back then to that region were supplied with larger condensers. Both on 134 are not impressive. They just cool and not freezing. I do not know how the temperatures get in the States but here humidity levels during summer start from 70%.

My initial post was for the SE where EVERYTHING imagineable has been replaced when the 134 conversion was done. The new compressor I installed (sanden SD5 S14) has 5 cylinders compared to the original denso which has 10 cylinders. Could this be the reason for the slower cooling and vent temperatures only reaching 60 Fahrenheit?
 

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560SEC 1989 Smoked Silver ,Burgundy Interior
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you have to make sure that you flush out the system with a very good ac flush starting for the lower end, then you have to blow it out with a compressor for at least 20 minutes, then you have to let it dry for 45 minutes or more, now you're ready to put in all the new part a new dryer is imperative and new oil into the system, changing all the seals for the new gas is a must, make sure you replace to an upgrade valves so you can inject the new gas
 
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