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

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, 159K

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.

CRAPOLA!!

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Norm in NJ
Next oil change at 230,000miles

Ditto. And even if it does harm the ozone, it only does so if it escapes the system.

To add to Larry's comments, if it's identified as r12, then you can probably assume no conversion was done. But if the refrigerant is identified as HFC-134, you really don't know if the original mineral oil lubricant was flushed out during conversion, and there would be still too many question marks to do anything less than a flush during repair.

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95 E320 Cabriolet, 159K

So many people asking how many pounds it takes to charge a system. It's not really determined by weight or even pressure, but a fairly straightforward graph that shows the relationship between pressure & temperature in the system.

You can probably "sneak up" on the correct charge by adding refrigerant while the car is running, watching the pressure switches turn on the compresser and then monitoring the temperature of the air being blown into the car. Leak checks are important as is using the correct lube for the refrigerant.

You can read the manual for the certification test for **free** at epatest It explains all this in excruciating detail. The section 609 stuff is for motor vehicles.

Cool,

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Norm in NJ
Next oil change at 230,000miles