R12 to R134A - PeachParts Mercedes-Benz Forum

#1 10-13-2003, 03:19 AM

After the car is back together I plan on converting to 134A. I was planning on changing the compressor, drier, and expansion valve. Is it necessary to replace these componants if they have not failed? I also remember that I was having problems with my climate control. It seemed to blow hot air whenever it wanted to causing the A/C to not work very well, or no heat when it was freezing. Occasionaly it would work good. Not very sure where to begin looking. I do plan on changing all the vaccum lines in the engine compartment when the engine goes back in.

#2 10-13-2003, 03:20 AM

Almost forgot, the car is an 85 300D turbo.

tjohn · #3 10-13-2003, 07:59 AM

Ack, another A/C thread. If you use the search function you can find a lot of info on this subject. To quickly answer your questions: 1. The only thing that absolutely needs to be replaced is the drier. Any time the system is cracked open you should replace the drier. Many people will replace the expansion valve, and compressor on a R134a conversion b/c the oil used w/ that refrigerant turns into something pretty acidic if there's any moisture in the system. Therefore, a leak typically means that you're asking for trouble down the line.

Have you considered simply fixing the leak and keeping R12 in your system? Your perfomance will be much better as you really can't get optimum R134a permforance in a vehicle not designed to use it originally.

Please note that you will need to evacuate, thoroughly flush your system (especially if you've had compressor failure) and vacuum it down to remove all moisture before adding refrigerant and oil.

Finally, the heat issue is a common one. Your monovalve probably failed. Again, a search will get you all the information (and probably pictures) that you need.

Good luck.

leathermang · #4 10-13-2003, 08:43 AM

TJohn is correct that you need to do a search... as a huge amount of information has been posted on this...
But you need to check on the expansion valve also... for my 123 there is an R12 valve and a 134a valve and you want to use the one that matches your refrigerant if there is one available....

gsxr · #5 10-13-2003, 12:28 PM

I'll make it simple. You live in Stockton. If you want to stay cool in summer, DO NOT UNDER ANY CIRCUMSTANCES CONVERT TO R-134A. There, is that clear enough for you? Please don't cite the "high cost" of R-12, you can buy it all day long for $20/can (or pound) if you check around eBay and the internet. Doing a proper 134a conversion is VERY hard and nobody ever does it right, when you're done it's much less efficient and almost useless over 100F ambient temps (you DID say Stockton, right?), and finally it's even more difficult to convert back after you pollute your system with that evil, horrible PAG oil.

Use the "search" feature, you'll find more than you ever wanted to know. BTW, in your climate, the only alternative refrigerant I'd consider is R-406b. Almost everything else (besides R-12) will have performance issues above 100F, with one or two exceptions. And no, Duracool won't work either in that kind of heat, no matter what that "redfox" bozo says.

:p

/rant

#6 10-13-2003, 01:21 PM

I live in west central FL. and YES duracool works and works fine. Street temps EXCEED 140 in the summer and I stay cool. Trick to duracool is you MUST ignore charging pressure and use VENT temps when you charge the system. R12 is the BEST way to go but if like me some ********* had convinced the previous owner to switch to 134 it is the ONLY option to consider since it will work with ANY oil. The work and cost of switching back to r12 stopped me from going that route. You have an r12 system now so if possible stay with it. If not possible look at duracool as it works and works quite well. You WILL NOT blow yourself up. This is total BS and if it happened as much as "some people" on this list tell you it would the sellers of the stuff would be locked up by now and charged with murder. We are talking about 12 ounces of flammable gas in a car that has 7 qts of flammable motor oil, 20+ gallons of diesel fuel, and several ounces of brake fluid under the hood that could also burst into flames in an accident.
My 300d had 134a in it when I bought it. My kids 240d had been converted as well but the old style York compressor sounded like it would fly apart when it ran. I read all the info out there on different stuff and tried the duracool last year. When I looked at vent temps way colder than what the 300d put out as well as pressures about 1/2 of 134 in her car I decided to convert my 300d as well. Vent temps went down 20 degrees in my car and the pressures went down 1/2 as well. You can't feel the compressor "hit" in the 300d anymore when before it felt like an anchor had been dropped when the A/C came on.
Screw the it's illegal in many states to use a flammable gas to charge any system. It has been many many years since I took the governments word at face value when it come to what is in my best interest.

Rick Miley · #7 10-13-2003, 02:11 PM

Way to go, Dave!

Well, May was A/C month but cumminsnut wasn't here yet, so I guess we can cut him some slack. If you're concerned about the certification required to purchase R12, don't be. It is almost trivial to obtain for $15 at Imaca.

gsxr · #8 10-13-2003, 02:37 PM

I'm pretty sure Stockton summer temps are above Florida temps most of the time. Stockton, IIRC, will get to 105-115F in the summer - same as Sacramento. Florida doesn't often get over 100F ambient (?), but they do have higher humidity. At least that's what I remember from visits to my relatives there years ago.

The dropoff in performance with Duracool (and similar products) gets more severe the hotter it is. It might be tolerable at 100F, but at (for example) 110F, ugh. Then again even an R-12 system is struggling at those temps. Mercedes seems to have undersized the AC systems in most of their cars, even the newer ones. Probably because Germany doesn't have bilstering heat like certain US states do!

#9 10-13-2003, 10:00 PM

very true that S. CA temps will well be above those of the "Sunshine State" as far as true air temps and I don't know what if anything humidity has on the A/C system. I am going only by experience with duracool here. I know that it keeps me cool here and will about freeze me out of the car when it's in the low 80's.
You said you wanted to convert to 134 and as many have said it is not a good idea with these cars. Trust me it does NOT work in FL. daytime May through October and would be just as bad in S Ca. Keep your car r12 or at least look at the alternitives on the market. 134 runs at pressures your A/C system was NOT designed for and will result in premature faliure. If my cars had not been converted to 134 using PAG oil I would use r12. Now the hassle of flushing and replacement of key parts keeps me either running 134 or duracool.

jhal · #10 10-13-2003, 10:49 PM

I live in Central Florida and my 300D was "blessed" with a proper (is there such a thing?) 134a conversion when I purchased it. Two words, it sucks. I just received my 609 certification from MACS (Moble Air Conditioning Society) to legally purchase R-12, and I am slowly getting the parts and materials together to make the system "right" again. Since at the moment, this my only car, I have to plan because it will probably take the better part of a day to reverse convert because of everything I have to do to insure a leak-free system that won't self-destruct from contamination. Listen to what everyone says and if at all possible repair your system and keep it R-12. Ok, I will shut-up now.:p

cracker928 · #11 10-20-2003, 11:58 AM

Hey guys,

I am from Palm Harbor, Florida and now live on the edge of the lovely Mojave Desert in California. It's HOT out here!!!

Anyway, my '87 is in need of a new compressor, and the local shop says the the bill would be $1000 for compressor, drier and EV replacement. They cite about 430 bucks for the compressor(insisting that it would be a new part, not rebuilt) and 4.5 hours labor. This would be using r12. Does this sound like a fair estimate?

Also, this has gotten me wondering about the r134 conversions, but I have read of very few good results with that. My '93 blows very cold out here and I was wondering if using an updated condenser might make a 134 update work well. As I type this I am realising that it might be just as costly now, but down the line might save some trouble.

Thoughts anyone?

Habanero · #12 10-20-2003, 12:57 PM

I am not trying to stir up what seem to be heated opinions (pardon the pun), but I have always worried about the safety of flammable refrigerants in a diesel vehicle. There probably isn't enough refrigerant in the system to worry about, but I always wondered if a catastrophic leak would create a runaway engine scenario. I have heard of caterpillars hitting propane lines which fed the engine too much fuel, thus blowing the engine. Anybody think this would be a valid worry on our vehicles?

Rick Miley · #13 10-20-2003, 01:03 PM

That sounds like a very fair price. I once paid $1800 for the same job on a 1987 300E, and that was using R134a. (Converted by previous owner

) It lasted 18 months and 30K miles before I had to buy yet another compressor. Bought that one from the dealer for something like $800. BTW, the R134a never worked well in that car.

jhal · #14 10-20-2003, 07:51 PM

Habanero, it is possible, under the right circumstances that a sudden large leak close enough to the air intake could cause the engine to runaway. Whether or not any damage occurs would probably depend on the concentration of flammable refrigerant and whether or not the motor is under load. Could you imagine sitting in traffic and this happening? Try explaining that to the cops!

william rogers · #15 10-21-2003, 02:09 AM

R 134 works fine in the North West and we do get hot weather in July and Agust,But of course not like CA or central FLA where I last lived. R134 sure is easy and cheap to maintain............
William Rogers.......