1982 240D AC

If the AC in my 1982 240D is working I sure can't feel it. At least not much cold air is coming out. I took it to my local mechanic who will check
it out. But he said that since it uses old coolant it would probably have to be "converted" if there's a problem. Does anyone know what I'm looking at, both in cost and potential problems/issues with such a conversion? I live on the Oregon coast so it's not as if I really need AC but it's nice to be able to unfog the windows quickly.
Thanks all,
Peter
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He is right... Your car if not converted, is using the R12 refrigerant. Conversion is simple and you should do it yourself if you have some mechanical skill or a friend who does.
You can go to autozone to rent a vacuum pump for free... Vacuum out the AC system for 45 minutes and then use the R134a conversion kit... about $40... and install everything in it... I believe they give you about 24 oz of refrigerant... you will need one more can of 12oz.... Not hard to do.
Because your system is under suction by the vacuum., when injecting new refrigerant, turn it upside down so it suck them in as liquid and see if you can get the second one in the same way... All you need to do is get the system up to 50 PSI or so to have the compressor kick on and then it will suck the rest of the refrigerant in.
You don't need engine running during the vacuum or the first can or two injecting...
One note... very critical... once the compressor is running... as the engine is running, you must inject the refrigerant as gas... so the can must be UPRIGHT. You are looking for the system to be at 30PSI and stable at that pressure even when the engine is revving... if it dips more than 5 PSI, you will need more refrigerant.
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My '80 M-B is still being cooled by R-12. Two years ago the price of old R-12 wasn't much higher than the new R134a refrigerant. So compare the cost of "topping off" R-12 vs. converting to R134a. R-12 is legal and available; it's recovered from old cars, refrigerators a/c units etc. There are EPA licensing restrictions on handling refrigerants; your man may not deal in R-12 so check A/C shops for someone that does.
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Update. My mechanic says I need a new compressor. No problem But he also wants to do a conversion to the new coolant. Total cost will be $900. Any opinions anyone?
Peter

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You are paying too much money for the compressor. You can get rebuilt compressor at much lower price from ebay.
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New Bear compressor part is $356. The rest is for the new coolant conversion kit and labor. I'm guessing I'm getting nicked on that.
Peter

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An option is a rebuilt compressor for half that. The local foreign car shop that has been around a long time and that I have reasonable faith in, says their experience with rebuilts vs new has been the same. Therefore, they recommend going with rebuilt. After the original failed in my 80 300SD, I had them put in a rebuilt. That failed catastrophically after about 2-3 years. At that point, I was skeptical about using a rebuilt, but they insisted their experience with them has been the same as new ones. I went with the rebuilt again, and here 15 years later, it's still running fine. You have to evaluate how much the difference would be in your particular case. And of course, there could be differences in reliability between your particular rebuilt and the ones my guy was using for my car.
Whether to convert to R134A or not depends on the current cost differential, how long you expect to keep the car, and where you think the price of R12 will be going in the future. As TG pointed out, I think today the price of R12 has come down from what it was years ago at the peak,
If you do convert, some of the issues are, R134A has a smaller molecule, so if there are any tiny leaks, it will leak out faster. And the system will have less cooling capacity, maybe 20%. Still adequate in my car for NJ, perhaps not if you were in a really hot area.
If it were me, I'd probably do the conversion with the new compressor. I did it on my 80 300SD 15+ years ago. After getting that last compressor put in 12+ years ago, she's been fine. Haven't put any additional charge in, except for a recharge 4 years ago, which was due to having to open the AC lines for other repair work In fact, right now it's blowing COLDER air then after the conversion. Which leads me to believe it may have been overcharged initially.

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I have a 1982 300 TDT. The AC on it went out about 5 years ago. The compressor went bad and I had it replaced.
The owner of the specialty AC shop I use in Las Vegas, Auto Air and More, will not use rebuilt compressors. He says that he has had too many reliability problems with them over the years, and so he only installs new compressors. The price difference is not much. You also have to install a new cleaner/dryer when you replace the compressor.
I don't know if it was because I changed the compressor and the system began to operate with greater pressure or if it was just the age of the car, but after I replaced the compressor the evaporator and condenser and 4 of the hoses began to develop slow leaks, so I had to replace those too eventually. I have spent about $2000 on my AC in the last couple of years.
At the time, the shop recommended using Freeze-12, which is a refrigerant that is environmentally better than R-12, but is compatible with the type of oil, mineral oil, that is used with R-12. Freeze-12 is a more efficient refrigerant than R-134a, but is still not quite as good as the old R-12. R-12 works well enough to keep cool in Death Valley on a hot day. I am not confident that my system would work that well with R-134a.
I live near Death Valley where we see temperatures in the 120 F range nearly every day from mid June until early September, so AC is necessary here.
http://www.freeze12.com /
At the web site above you can purchase Freeze-12 in kits that allow you to recharge the system yourself. EPA regulations allow anyone to work with Freeze-12. You have to have a license to work with R-12, so Freeze-12 also has the advantage of being able to do it yourself.
If you do change over to R-134a you have to make sure that you purge the system of the oil that was used with R-12, because R-134a is not compatible with mineral oil, and it supposedly turns into a gel in your system if they combine. I have not tried it myself, but a local mechanic here told me he put 134a in one of his cars without purging the system and it worked fine. But I would recommend Freeze-12 anyway, and so does he. Like I said, with our weather here AC is a vital necessity. You can buy the cans of Freeze-12 at any NAPA shop around here.
Here is a routine for filling the system. It sounds mysterious at first, but read it a few times if necessary, and it will start to make sense.
You only need about 95% as much Freeze-12 as R-12 because the molecules are different in size.
Jon E from Prescott, Arizona (337 days 23 hours ago.) Once your system is leak tight, contains the proper oil to match the refrigerant to be used, has been evacutated to remove any air and moisture contained therein, and has a metering device designed for the refrigerant to be used, then one may charge the system thusly:
1. Attach the refrigerant container to the low pressure (suction) side of the system. 2. Open the refrigerant container, thereby breaking the vacuum, and allow as much refrigerant to enter the system as will go into the static system. Then, shut off the valve to isolate the refrigerant container. 3. Place a floor fan in front of the car so that air is directed against the condenser (located in front of or is part of the radiator) to simulate ram air (the air flow generated by a car's movement). 4. Start the car and adjust engine speed (weight on foot feed?) to approximate approximately 40 mph. 5. Place an accurate AC type thermometer in an air discharge duct which has the best air flow. 6. Turn on the AC. 7. Open all the car windows. (Note that the car needs to be in a warm environment of around 90 degrees f for charging to work best and most accurately.) This keeps the heat load on the evaporator (cold coil in the car). 8. Check the thermometer continuously. 9. As refrigerant is added, the temperature will come down for so long as the evaporator is not completely full of refrigerant. 10. Go easy, adding a little bit of refrigerant and waiting upon the system to equillibrate. 11. If the temperature drops, add a little more refrigerant and wait and watch for drop or not. 12. As soon as you notice that the addition of refrigerant has not caused any temperature drop, you have the system charged to the point where the evaporator is maximally used. STOP adding refrigerant at this time. 13. Dismantle your setup and you are ready to drive a car with a properly charged system.
This works with any refrigerant.
Note that R-12 could be charged as either vapor or liquid, with the caveat of not slugging the compressor valves with liquid. R-134a and other azeotropic refrigerants separate in the gaseous state and must be charged as liquid. Their cans are designed with dip tubes so that liquid comes out when the can is upright, just opposite of R-12 cans. Again, don't slug the compressor. That requires metering the liquid through a small oriface, which are available as individual divices, or by cracking the container or gauge-set valve and thereby causing the liquid to flash into vapor before entering the system.
I am not an auto mechanic, but an old retired HVAC tech who understands the physics and has charged all my autos thusly and those of my friends. Prior to this method, I tried all the other methods, such as, sight glass, pressures, and weighing it in. No method worked better or as well as this method.
As for converting a system, I beleive (as best as I can remember) that the oil and the meteing device should be changed when going from 12 to 134a. All systems should be vacuumed, although smaller systems used to be "blown out" with the refrigerant by many techs. All other considerations aside, that practice absolutely is illegal today.
If a system is empty when you start working on it, it needn't be recovered, but if any refrigerant is in it it must by law be recovered and properly disposed of, as must the old oil. Also, for residential and commercial systems, you by law must hold an EPA certification to open a system. I believe there is an automotive certification, but I am not certain if it must be held to work on automotive systems.
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I've been checking some online sites about R12 vs. Freeze 12 and there are some pros and cons about it. Do auto AC shops still use (recycled) R12 and could I have the new compressor put in, have the system refilled with R12 and drive happily down the road? I'm not crazy about straining the compressor with the R134a
Peter

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What does your current guy say about just staying with R12? AFAIK, at least some AC shops are still recharging with R12.
As to whether you will be happy with it driving down the road, that depends on the price of R12 vs R134a, the continued availability of R12 for however many years you continue to own the car, and whether it will need to be recharged again for whatever reasons while have the car. Since you're going to have the system open, install a new receiver/dryer, recharge, etc, you've already taken most of the hit for converting to 134A. In fact with the price of R12 vs R134 it may be the same or cheaper to go with R134.
I don't understand the concern about "straining" the new compressor if you use R134a. I've never heard any problems specific to compressor longevity, as long as the conversion is done correctly.
I've had a rebuilt compressor with 134 going now for 12 years+, no problems. The main issues are the conversion needs to be done correctly and you may have about 20% less cooling capacity. I''ve also heard people who noticed no difference. Once concern was that the older hoses would leak the smaller molecules. This doesn't appear to be a problem and I've read that it's probably because the mineral oil in the R12 system made it's way into the old hoses, effectively plugging them up so the R134 molecules can't escape. Whatever, in my car there have been no recharges other than the one 4 years ago which was because the system had to be opened for other reasons.
I went with the rebuilt because at the time, there was a substantial difference between the rebuilt and a new one and the shop stated their reliability had been the same with new vs rebuilt. I would agree with Heav that if the diff in your case is relatively modest, then I'd go with the new.

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