AC Question/R12 vs R134 - PeachParts Mercedes-Benz Forum

Rockman59 · #1 05-26-2009, 03:16 PM

My '86 560 SEL has the stock AC system with R12. I have always recharged the system every 5 years or so and always with R12. Today when I went to my indie MB shop that I have been using for many years they told me they were going to use R134 for the recharge. I asked how was that possible as everything I have ever read about AC systems says you cannot charge with R134 without making many modifications. The shop owner assured me that R134 would not hurt my AC system. I told him if there was a problem adding R134 to the system he was going to have to fix it. He said he would fix any problems and again assured me that everything would be OK.

Comments please.

david s poole · #2 05-26-2009, 03:26 PM

if you want a/c that will only have 70% of the power of the r12 go right ahead[after flushing out the old oil and replacing with oil compatable with 134] and don't forget that because the molecules of 134 are so tiny you will need all the hose replaced with barrier hose or look forward to a recharge every year.

CWW · #3 05-26-2009, 03:41 PM

Your indy is wrong, I would go somewhere else for a/c work from now on, or insist that he use R12.

To begin with, you have to flush the system to remove all the old mineral oil, then replace it with the newer synthetic oil that is compatible with R134a. Then, you have to change all of the refrigerant hoses in the car, or else you're going to need to recharge the system every time you turn around, as the unlined hoses in an R12 system will allow R134a to escape easily. R134 requires lined/coated hoses.

And if the cost and aggravation of all that isn't bad enough by itself (it is), then be prepared to have an a/c system that only works half as good as it used to. R134a is less efficient than R12. The 134 will never come anywhere close to the performance you are used to out of R12. If you live in a hot climate, you will not be happy with the result at all.

I would absolutely NOT make this switch. It's not going to give you the performance you're already used to. As another member said, it will only work maybe 70% as well as the R12 did, and I think he's being pretty generous when he said 70%. I've had both 12 and 134 in my W126, and I would personally say the R12 worked closer to 2x as good as the 134. And the part about being able to just suck R12 out and put R134 in, without doing anything else is just wrong. I mean, yes, physically you can do that, but it's never going to work right. Your guy doesn't sound like he knows what he's talking about when it comes to conversions.

spree17 · #4 05-26-2009, 03:49 PM

Where can we find out how many cans or ounces of r-12 is needed to recharge an empty system?

david s poole · #5 05-26-2009, 03:58 PM

most of the older r12 systems held 30-39ozs of refrigerant so between 2 1/2 and just over 3 cans.

spree17 · #6 05-26-2009, 04:11 PM

Thank you David.

Rockman59 · #7 05-26-2009, 05:27 PM

In reviewing my service records I found an invoice from 2006 for an AC recharge. At that time I assumed they would use R12 as that was what was in the system. Wrong!!! In the fine print on the bill I noticed I had been charged for R134....it appears I have been using R134 for the past three years and did not even know it. I called the owner and let him know how I felt about them arbitrarily switching to R134. I would not have let them do it had I known. I told him I was holding him responsible for any damages that may occur to my AC system. I have been using this shop for almost 15 years and they have always been very reliable, honest, and reasonably priced. The original owner sold the shop about three years ago to his service manager who is the owner who I spoke with today. Looks like I am stuck with R134. I will keep a close watch on the AC...it is blowing cold air today. I have a hunch that within a year my indie dealer with be doing some "warranty work" for me. He has been put on notice. I know he does not want to lose me as I have been a valuable customer to him for many years. I'll let you guys know how it turns out. Thanks for all your input.

ah-kay · #8 05-26-2009, 08:30 PM

Quote:

Originally Posted by Rockman59

In the fine print on the bill I noticed I had been charged for R134....it appears I have been using R134 for the past three years and did not even know it.

Did you notice the difference with the AC running on R134a without knowing it? It would be hard not to notice if R134a was at 70% or 50% efficiency as some members pointed out.

Rockman59 · #9 05-26-2009, 08:41 PM

Thinking back, my MB never had really cold air...and I think that is pretty common, at least on the 560 SEL models and other models of that era. But yes, it did seem to me that the AC was even less cold for the past few years since the R134 was put in. I probably rationalized this as just standard MB "not very cold AC". After they recharged the system today the air was blowing much colder than it had been....probably because the system was low on R134 because of the slow leaks through the R12 hoses as has been mentioned in this thread. Needless to say, I was not happy finding out that I had been converted to R134 without my permission.

Uncle Acky · #10 05-26-2009, 09:29 PM

From what I have learned R134A is a very poor replacement for R12 and to make matters worse it is only marginally better for the environment. When you factor in all the botched up AC systems that some (not all) users end up with, much of this stuff ends up in the atmosphere....much more than properly maintaining R12 systems. The host of other Freon blends are also cr@p for the most part IMO.

My 92 w124 had R134A when I bought it for my wife and it had the condenser blow and that was the end of it. Head pressure is greater than that in an R12 system.

I searched for a Freon replacement for my 90 w124 and tried Red T? it was garbage and did not cool at all though we followed installation/conversion instructions to a T.

I searched some more and found SP34E {Liquid charge ONLY} {80% to 90% of R12 charge} for me it was a direct R12 replacement. The system was properly evacuated and charged, it works very well but it has only been in for one year.

I do think that many AC systems are damaged when some people who lack proper tools, equipment and experience try to work on or diagnose rather complex AC Systems. I have also heard QUOTE " my buddy fixed my AC, he knows a lot about cars but now it doesn't work eh?

I didn't actually mean to write all this, oh well,
Acky

spree17 · #11 05-26-2009, 06:44 PM

Ive been considering trying out one of the alternatives to r-12 and r134a

spree17 · #12 05-26-2009, 10:33 PM

The 2 alternatives I have heard the most good stuff about are freeze 12 and Envirosafe ES12a

mbbuff · #13 05-26-2009, 11:02 PM

My son, a mechanic for 30 years, says that Freeze 12 is totally compatible with R12, and works just as good. I still have about 6 lbs. of R12 so haven't tried it yet. I did switch my Jeep from R12 to R134, and as said earlier, it's barely half as good. My son said that if they don't change the compressor oil (which many don't) it will be worse yet. Only remedy is to flush, reservice with the proper oil, and use the corresponding freon.

Hit Man X · #14 05-28-2009, 02:36 AM

Quote:

Originally Posted by mbbuff

says that Freeze 12 is totally compatible with R12, and works just as good.

Put it in an MB (such as this 560sel) after running R12 and let me know what you think. It doesn't cool nearly as well, especially in a volatile climate. Well basically from the middle of the 48 on down.

These cars were designed in Germany, ever checked the latitude of Germany vs the US?

Hot days to them are not hot like they are here.
Girlfriend of mine lives outside of Moscow, how to her is in the low 80°F area. That's downright pleasant to us.

MB updated the AC systems constantly in these cars just like BMW did with the E23s of these years. The condensers early were inefficient, so they doubled the tubes for more surface area to dissipate heat (same capacity) around 1985 from what I gather, the aux fans were tiny on the early cars (again, became far larger) these grew around 1984, heck then in 1989 AGAIN MB changed the condenser fan and went to dual fans.

Quote:

Originally Posted by alabbasi

Not sure why anyone needs to convert to R134. R12 is getting cheap these days as fewer cars are using it. I have 4 cans on Ebay for $80.

R134 is the only alternative to R12. Anything else will be a gamble and no shop would knowingly touch your system with a recovery machine if they knew you had put some sort of snake oil in it.

Before anyone says Freeze12.... Freeze12 is 80% R134 so it's not a direct drop in as it's 80% R134 so it won't mix with the oil so R134 is the only real alternative.

Can't agree more. I tried F12 in my 300sel only because the system supposedly had an evap core leak, it doesn't. So I need to... uh.. have it recovered then recharge it with R12. Cooling is very poor with it unless running down the road, then it's decent.

I have multiple tanks of R12, it's just NOT that expensive to purchase in large quantities (sub $10/lb... that's nearly on par with the 134A at the auto stores). Hell, even like what Al is selling is plenty reasonable @ about $25/lb... a properly rebuilt system shouldn't need an AC service for easily a decade. I'd buy two, maybe three setups like Al is selling and be covered for a while if I had to have my car serviced somewhere.

LASTLY, you guys doing AC work in the summer are going to get reamed. This HVAC stuff needs to be done in the off-season so demand is low and you'll get better pricing on parts and/or labor.

Matt L · #15 05-27-2009, 12:49 AM

From what I've read, HC blends work well in R12 systems, although not quite as well at idle. Better at idle than 134a, I'm sure.

The problem with HC blends is that it is illegal to convert directly from R12 to HC. Since mineral oil is miscible in HC liquid, it would be ideal to extract the R12 and charge right up with HCs. It would be better for the environment than 134a. But it's illegal and the penalties are quite severe.