How Do I know if my AC system was converted from R12 to R134?
 

The car is 91 420SEL.

Also, another stupid question. What would happen if R134 was added to the R12 AC system?

THanks

bad things if they are mixed....due to lubricant issues acids can form and eat out the system from inside-out.

Here is the thing.

Stupid me!. I inherited this car. The engine was removed for overhaul and reinstalled. The AC system was completely discharged. Without thinking and knowing whether the AC system is R12 or R134. Stupid me went ahead and recharged the AC system with R134 2 days ago and the AC has been working great.

Let assume the previous owner changed it to R134 then there is nothing I should be worried about. The problem is, HOW CAN I TELL IF IT WAS CHANGED to R134?

If the R12 system was not converted to R134. WHAT DAMAGE HAVE I DONE and WHAT SHOULD I DO?

PLEASE HELP!

Short of having a refrigerant identifier instrument, you cannot know for sure if you don't know the history of the car. By US Federal law, the car is SUPPOSED to have the correct fittings, but zillions of cars get converted to all kinds of refrigerants without changing fittings.

Yes, you can put 134 in a system and it will likely cool great. The problems will occur later. Depending on the conversion even one that is considered to be converted correctly is almost sure to have problems in the future.

R12 has come down in price and 134 is going up. There is very little difference now, in the price of the two. If the car were mine, I would break all connections and flush everywhere to get all the oil and any debris that might be present out of the system, replace the r/d, put in about 8 ounces of mineral oil, evacuate it and then charge with R12. That is the only way you will have a system with a good chance of staying in good shape for the long term.

If you insist on staying with 134, please do it legally with a sticker, the correct fittings and make sure it has the correct amount of ester oil and has been properly evacuated.

Good luck,

The A/C connections are completely different, R12 are screw on while R134 are push on, like air tools. There should also be a blue sticker somewhere on an A/C component, like the accumulator, detailing the conversion date.

Look at the A/C refill connectors first.

I suppose that I was not clear in my previous post.

There are ZILLIONS of cars out there with original R12 fittings, no adapter fittings and no sticker that have 134 and all kinds of other refrigerants in them. This violates US Federal law, but they're plenty of them out there.

The only way to know for sure is to connect a refrigerant identifier instrument. DO NOT assume that it is R12 because there are R12 fittings on it.

Now that 134 is going up in price the same now holds true for a car with 134 fittings. There could be anything in there.

The people who are to be thanked for this are those who are either ignorant of the law or choose to break it.

Have a great day,

I concur....my W116 has all the lables showing R134 conversion but it still has the R12 fittings....if that sticker was gone I would never know. Once I get my guages and stuff and get certified to Purchase some R12 I will Fix my W123 and flush my W116 and redo it with the Correct R12.......and damned what any technicalities say.

I have a vacuum pump now and looking for the other tools needed at the right price.

Wish I could borrow them local for a week or two when the time comes. I can't afford to pay someone to do the work.

Thank you very much for your replies!!!

I am one of those ignorant kinds and did not mean break any laws intentionally and not even sure what kind of laws did I break. Please educate me. What are the US federal laws for this and what are the reasons behind it. I thought the only reason was because the R12 was too expensive and inferior to R134 that people change it to R134. If the only requirement to change to R134 is to have the correct fittings then why aren't people doing it? Are these fittings expensive and involve a lot of labor to change?

What is the r/d?

what kind of problems will occur later if R134 is used in the R12 AC system?

I am going to have to shop check into it and do it correctly. I will have them change it to whichever system that is the least expensive.

Thanks again!!!

What does it cost today to have a typical MB AC system, with R-12, serviced, including, flushed, re-lubed and filled again with R-12?

Mine is working Ok, but I have no way of knowing if it remains fully charged from 4 years ago! .....BB

There have been volumes upon volumes upon volumes written and debated here regarding the refrigerant issues. A search should turn up way more than you ever wanted to know, but I will try to summarize your questions.

R/d is the receiver/dryer. It should be changed whenever changing refrigerant types or if the system has been opened for serious work.

The two most immediate problems in changing to 134 are a 15% loss in cooling capacity. Some cars are more sensitive to these than others. The second problem is that the oil that circulates with R12 is not compatible meaning that it will not circulate with 134 thus wearing out the compressor.

When changing to 134 properly, you need to change to the appropriate fittings to remain legal, change the r/d, flush the entire system to get out the old oil, put in the correct amount of ester oil, evacuate and charge.

For an R12 system that is staying R12, you should not flush and recharge as a preventive maintenance step. The a/c system is unlike most anything else in that doing such a step will probably create more chances for a problem because of the chance of introducing moisture to the system which combines with the refrigerant to make an acid. That is why the system must be evacuated any time it is opened up.

For an R12 system, when it quits working, it has probably leaked out the refrigerant. At that point, you find and repair the leak and if the system has not had an r/d recently, you replace it at that time. Then you evacuate and recharge. You also replenish any lost oil, this is done according to the component replaced.

Hope this helps,