The recharge connectors are different between R12 and R134a. R12 are screw on, R134a are pushon similar to air hose connectors.

If the car was converted to R134a, the expansion valve would have been changed as all the O-Rings. There would be a blue lable with a date on it.

You cannot add R134a to an R12 system.

http://freeze-12.com/

http://www.supercool.ac/intro2.htm

http://www.acsource.com/index.asp

http://dieselgiant.com/index.html

A DIY page

http://dieselgiant.com/repairyourac.htm

In response to the questions about how many cans of Freon. In the past you would just view the sight glass and watch the bubbles. When the bubbles went away, it had a sufficient charge of Freon. If you suspected the Freon was low, you just looked at the sight glass.

Has it changed now for the older cars with Freon? My 81SD has a sight glass and still runs Freon and feels like a meat locker.

This is the method that I use with R12 systems. I don't think that it applies with R134 systems or systems that have been converted to R134. You're better off hooking up the pressure gauges and making sure that it's filled to the right pressure.

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? :eek: :D 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.



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.

I got tired of the wondering every season if my A/C was going to need work in w126 and had my entire system gutted and professionally converted to 134. Every part of my system was replaced including the compressor and anything that touched freon such as hoses and other parts. I decided to do 134 because its more likely to be readily available in the future and with replacing everything I had the opportunity to do a proper conversion. My A/C is ice cold and comparable to the A/C in my w140 even though the w140's system is a superior design.

I think a lot of the misinformation about 134 is due to leaky systems that people just put a charge on without completely sealing and cleaning the system. The unfortunate truth is if you want really cold A/C your going to likely need the assistance of a professional that's able to correctly seal your system and get any moisture out of it with a vacuum pump. Pumping 134 into a leaky system with moisture in it would have a similar effect to doing that with R12.

People who willfully pump R12 into leaky systems because of cost are the reason why we had to change to 134 to begin with. Karma is a wonderful thing though. That moist sort of cold air must be great eh?

And what are your vent temps on 134? Idle and cruise?

How many thousands did you spend to do this? Two? That will buy you nearly a few hundred pounds of R12. Will you actually be driving that car in 10 years? 20 years? Probably not, but maybe. A 30lb tank of R12 would last that car pretty much until you and I are not able to drive anymore.

I used F12, basically 134 with a few other bits within. System was totally rebuild last summer by ME, including expansion valve, orings, compressor (obviously), etc. The performance is decent when cruising, but lower speeds it just lacks big time in the 300sel... I have R12 in my other stuff, I'll compare to my MBs only for sake of discussion, in my 300SD, SDL, and 560sel, the performance is just far better due to the limited capacity these vehicles have to begin with. Going from 2.9lbs to 2.3lbs is a large drop in capacity... this is because, 134A is less efficient! New vehicles have updated condensers/evap cores to compensate.



Aside from certs, I think there are more than a few people (including myself) that have the knowledge and skills, and own the tools, to properly rebuild an AC system on these cars and others. I've rebuilt close to a dozen now (stuff from the early 70s to mid 90s), there's not much to them. It's like assembling an auto trans or building a valve body. Take your time, keep it clean, and be patient. Biggest of all, don't rush or use crap parts.

I rebuilt the one in my '88 F150 back in 2000, it's still working great to this day. This was my first one done.



The mandatory conversion for auto makers to 134A is largely debated, it's more than ozone depletion... 134A does almost the same job at depletion FYI. Dupont's patent expired/was expiring on R12 in that time frame too FYI.

Have not really had the need to measure the temperature. At least as cold as my W140's A/C if not colder. With the temp set to 22 on the wheel the car cools as quickly as my W140 even after sitting in the sun (both of my cars are black).

I have owned the car for about 7 years and plan on keeping it for a very long time. Recharging year after year and wondering if my A/C was going to make it though the summer was getting quite old. The system in the car was 27 years old and really needed replacement.

The cost was more reasonable than I expected but the figure is between myself and my mechanic. If I had known I would have seen this level of improvement from an overhaul of this level I would have had it done 7 years ago.

When you consider the cost think of how much it costs to diagnose and repair a system every few years versus doing it right and having a better performing more reliable system. While some people have the false sense of savings by doing their own work how much is your time worth?

I don't think anyone here is suggesting using R12 or any other refrigerant in a system that is known to leak. That's like throwing away good money after bad money.

Problem is that a half done conversion to R134 or any of the snake oil on the market is that it will probably create leaks in what was otherwise a good system.

You got sold a bill of goods, man! R12 is still being produced overseas, you just can't make it in the US anymore. The whole "it's going to run out" in the future thing is total B.S.

And R134 isn't any better for the environment than R12, it's also highly toxic. I'm not really sure what the government thought they were doing when they started forcing the switch. In any event, the government has really backed off the whole R12 ban thing anyway, they don't seem to care about it now. It takes 30 minutes to get a refrigeration license online and buy and install it yourself. All the a/c shops around my area have no problem dealing with it either.

Not at all. I won't be under the hood next year trying to figure out why my A/C is lukewarm. I overhauled my system mostly because it was tired and 27 years old. Picking a modern refrigerant that has a higher probability of being easy to find in the future made sense for me. You can get R12 now but what about 10 years from now when many of the R12 cars have died off or have been converted? I plan on keeping my car long term.

I converted to r-134 but I do not like the results. What is the minimum I would have to do to go back to r-12 and have it work?

Perhaps not intentionally but with limited tools and budget many shade tree mechanics are doing just that. I assume everyone here has their own R12 recovery systems and vacuum pumps right?

I think you hit the nail right on the head. In order to convert correctly to 134 parts need to be replaced and money needs to be spent. The shade tree approach of charging with 134 and slapping a sticker on under the hood does not work quite so well.

As the owner of a '93 2.3 and still using R12, what procedures did you perform when you converted to R-134a?

I believe my system was empty when I bought the car. I put in a new drier, new fittings, new oil, new freon and a new label around 4 years ago.

Thanks for the reply,

I've heard from other forum members that have had good/decent luck converting to R134a by basically doing what you've described, including vacuuming the system. One important factor was putting in the correct amount of R134a, since using the drier sight glass isn't the right way.