IIRC, the problem with the O-rings was caused by the R-134a compatible oil when R-134a was first introduced. After the first year or so, better oils (lubricants, to be more precise) were formulated and are now compatible with all normally used O-rings. That assumes they're in good condition, of course.

Personally, I've converted all of three American cars from R-12 to R-134a. Two were successes, one a disaster. If my 260E starts fading, I think I'll take the silly test and buy R-12 on eBay. Heck, that's how I bought the car.

Cool,

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Norm in NJ
Next oil change at 230,000miles

I had to replace my condenser and have my car charged up. In Ontario R12 is not legal for use. The shop that does my heat/AC work is topnotch and has never led me astray in the 10 years I have dealt with them. They only do heat and AC work, on anything that moves. I spoke with Doug about the issues that I have read about on this site and have been reassured that if it is done properly it is not a problem. He got my new condenser, a new dryer, cleaned one switch and replaced another, checked the system for leaks, vacuumed it and then charged it. To date it has worked very well, other than the fact that I needed to replace 4 of my vacuum pods. We have had two periods of extreme humidity with temps in the low to mid 40's, and it worked as well as my Jetta, and better than my Dodge. Perhaps some of the problem systems have not been properly gone over, OR I'm just living life right and mine works.(for now?) Andy

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1987 300D
1997 Jetta diesel
1998 Ram Quad cab

pmckechnie,

Yes, I did not know you were making a joke. Things are easily taken wrong from written text. It's a testament as to the importance of body language.

The chart I have indicates 2.66 pounds of R12 for your '84 500SEL. This is not factory information, but it is probably pretty close.

That said, R12 is not near as fussy about having an exact quantity as is 134. If you get it a little over charged, it will accumulate some in the r/d. If you can achieve about 22 low side and about 250 to 265 high side in 80 degree ambient with a fan in front of the car, engine at about 1500 RPM and after about five minutes for pressures to stabilize, you should be okay.

lyonstexas,

If you change from 12 to 134, you will be better served by using 134 compatible o-rings. These o-rings are good for BOTH 12 and 134. Used to these were green, but now there are 134 compatible o-rings available that are black.

You can get a very good assortment for about$25 from ackits or acsource and it comes with nylog seal lubricant. If you will doing even a small amount of auto air work, this will prove to be a good investment.

Good luck,

Thanks Larry

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84 500 SEL (307,xxx miles)

Try as I may, I cannot locate a shop that will rechange my R12 system in San Francisco. Everyone I ask only talks of the cost to convert to R134. I have a few pounds of R12, no one wants to touch it. I had a few cars with R134, none seem to cool as well as a R12 system. Is this difficulity in locating service shops common in California? Any recommendations.

How to deremine which R12 or R134 system on my 1987 260E (it is not working)?
What is default system for this model? How to find out if the previous owner did not convert it to another system?
Tnx.

Back in '87 a/c was charged with r12 at the factory. If it has been properly converted, it should have the new style fittings (quick-disconnect versus the old 'tire-valve' design). In addition, it should have a conversion sticker displayed conspicuously under the hood.

If you're not sure, take no chances and flush the system some time during the repair to remove the lubricant before recharging.

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95 E320 Cabriolet, 169K

1987MB260E,

You can go to an automotive a/c shop and they have a refrigerant identifier instrument that can be attached so that you will know for sure. As previously answered, your car was originally R12, but I have seen lots of cars with original fittings that have been illegally and improperly converted to God only knows what. Don't take chances. Have it identified. Not everyone converts them in accordance with the law.

Good luck,

the main reason for converting to R134a is that R12 depletes the ozone layer.

it's about good environmental citizenship, not operating cost.