Successfully converted w123 300TD Wagon to R134 - PeachParts Mercedes-Benz Forum

MercedesOtto · #1 07-14-2009, 08:59 AM

Observation:
As a result of the rebuild that is described below my AC works great with R134in the 95F heat of Atlanta Georgia. I believe the bad reputation of R134 in the W123 AC system or its weak functioning comes from underlying problems like not functioning vents, oil and or Freon over fill, cheap aftermarket compressor etc….

The following underlying problems I fixed on my car:
-hidden leak in dryer pressure switch (replaced switch)
-center vent did not open properly due to vacuum leak on vent actuator
-compressor on my car was a cheap aftermarket model
-auxiliary fan was working intermittently (I had to buy a new used one)

Rebuild procedure

1.System completely flushed with compressor and expansion valve removed:
On a 28 year old car it cannot be sure how much oil and what else is actually in the AC system - especially when a leak was present and for safety precaution oil was added here and there.
However since I wanted to try the R134 conversion anyways I cleaned all oil out of the system to replace it with oil that is compliant to R134. I used a syringe to inject cleaner into the lines and than used air pressure to blow it out to the other end. For the lines that end inside the car a big trash bag being wire tied to the other end of the line keeps the mess contained.

2.Assembly of system: I spend a good bit of time cleaning and fine sanding / polishing the O-ring surfaces of the lines. The o-ring seating surface was corroded and had slide pitting. I only discovered this at very close observation. I’m sure most shops would not have taken the time to do this.

3.Vacuum testing the system for leaks: when 29 psi vacuum was reach and stayed stable for a few hours I was confident the system was sealed.

4.Refill the oil: the OEM manual asked for 8oz oil total in the system. Since I cleaned all oil out I was confident that the 8oz was needed. Not flushing and cleaning the system makes the oil amount a guess. I filled the oil by disconnecting the line brake in front of the valve cover. (Careful if the system still has vacuum - the o-ring could be sucked :-( into the line) The oil was filled in the line leading to the compressor intake. I turned the compressor by hand every once in while to suck in and distribute the oil. Once the 8 oz disappeared the line was closed with a new o-ring.

5.Evacuation and filling of the system: A German friend that is specialized in working with W123 here in Atlanta offered me his advice, shop lift, tools and vacuum pump for this AC rebuild. Per his experience only 80% of the recommended R12 filling amount provides best results for R134. Well as always he was right. The AC works awesome!!

6. After half of this summer in the Atlanta traffic without AC it feels wonderful to turn the AC to lower blow because it is getting to cold soemtimes !!!!

7. The whole effort took me a long day (10 hours and ½ a six pack) with my friend’s expert directions.

Remaining issues:
The molecules of R134 are smaller and have the reputation to permeate through the old rubber lines. If my system has lost the Freon before the next season I want to replace the rubber lines as well. Based on what I have seen in this project it cannot be to much work.
My idea is to find the rubber lines and crimp caps. Cut and position lines to perfect fit and have them professionally crimped and pressure tested.

It would be great to hear from others that successfully use R134 in a W123.

MercedesOtto

dmorrison · #2 07-14-2009, 10:28 AM

82 300TD completely rebuilt and converted to R134a with a parallel flow condenser. 1.5 years later the compressor failed. Went back to R12 and no problems.

Dave

JimmyL · #3 07-14-2009, 10:31 AM

Quote:

Originally Posted by MercedesOtto

Successfully converted w123 300TDT to R134

First and foremost:

Anything you get out of R134a in these cars would be even better with R12 or Freeze12. I've gone through everything within your description, which to your credit is a very thorough rebuild of your AC system.
In 5 examples I've done, 3 with the complete process you describe above, R134a gives you less cooling, and does it slower than R12 or Freeze12. I currently have a W123 with Envirosafe, but it does not appear any better than Freeze12.
Also, working up to 95 degrees still doesn't cut it here. 104 today!!!!

I do commend you on your quality of work, and I'm glad it is working well for you. Very nice job. Just watch that rogue T.......

JimmyL · #4 07-14-2009, 10:33 AM

Quote:

Originally Posted by dmorrison

82 300TD completely rebuilt and converted to R134a with a parallel flow condenser. 1.5 years later the compressor failed. Went back to R12 and no problems.

Dave

Dave, have you found an engine for your wagon yet?

MercedesOtto · #5 07-14-2009, 11:34 AM

Quote:

Originally Posted by JimmyL

First and foremost:

Anything you get out of R134a in these cars would be even better with R12 or Freeze12. I've gone through everything within your description, which to your credit is a very thorough rebuild of your AC system.
In 5 examples I've done, 3 with the complete process you describe above, R134a gives you less cooling, and does it slower than R12 or Freeze12. I currently have a W123 with Envirosafe, but it does not appear any better than Freeze12.
Also, working up to 95 degrees still doesn't cut it here. 104 today!!!!

I do commend you on your quality of work, and I'm glad it is working well for you. Very nice job. Just watch that rogue T.......

Thanks for the interest and comments on my description!
Since I'm from northern Germany and not used to the heat so much I should be more sensitive... however my AC with R134 works well enough. (even my car beeing a Touring or like Americans say a wagon - the AC has much more space to cool!!)
I also have a 2005 Honda and the AC output is not much cooler. The only difference is really at idle and distribution of cool air to the back seat, that is much better in modern cars like my Honda.

I'm not clear about your "T" thing.

MercedesOtto

MercedesOtto · #6 07-14-2009, 11:46 AM

Quote:

Originally Posted by dmorrison

82 300TD completely rebuilt and converted to R134a with a parallel flow condenser. 1.5 years later the compressor failed. Went back to R12 and no problems.

Dave

We will see in a year if my compressor still works. I hope your experience was an exceptions :-).
Comparing apples to apples it would be interesting to know if your compressor was OEM or rebuild aftermarket ( at least it lived 1.5 times the warranty expectations)! Maybe the system had residuals of the old oil in the system. My friend that helped me with this project indicated bad experiences with rebuild compressors.

dmorrison · #7 07-14-2009, 12:01 PM

Everything the system was brand new. Compressor, condenser, hoses, evaporator, dryer,oil,freon.
R134a does not operate as efficiently as R12. The pressures will also operate higher for the same cooling ability. Located in the DFW area so we get some heat here. My conclusion is the R134a was the problem. Not the R12. The system ran fine after the conversion back to R12 including a new compressor and complete flush.

Good luck with your system. Many here have run R134a without problems.

Dave

dmorrison · #8 07-14-2009, 12:06 PM

Quote:

Originally Posted by JimmyL

Dave, have you found an engine for your wagon yet?

No I have not. I'm think I'm going to let her go. After it cools down I'm going to clean her up and sell her.

Dave

E150GT · #9 07-14-2009, 12:10 PM

I must be outta the loop here. What is rogue T?

rrgrassi · #10 07-14-2009, 12:17 PM

The MB's trunk show 300D or 300TD There is not an extra or "roque" T So, you will not see 300DT or 300TDT on the trunk, delivered from the factory.

Back to original Topic.

I tried 134a...was nice and cold when temps were in the 80's. 90's to 100's, it seemed cooler to just ride with the windows down.

zeke · #11 07-14-2009, 01:30 PM

I R&R my wagon compressor last summer and filled w/R12. This summer developed a leak in the high pressure line. I am going to reclaim R12 and convert to FRIGC - R12 has gotten too $$$ and it is becoming harder to even find the quantity I need from a single supplier.

I will let you know how it goes.....

KCM · #12 07-14-2009, 02:19 PM

Quote:

Originally Posted by MercedesOtto

It would be great to hear from others that successfully use R134 in a W123.

MercedesOtto

I have retrofitted a W123 300CD a few years back, as well as Ford products without problems or destruction. On the W123, replaced the Delco compressor with new, new drier, new expansion valve, new pressure switch, and new o-rings. Used the oil compatible with the R12 oil, filled it up to 80% to 85% of the R12 fill and it worked fine. Note: System was sealed and compressor had not self-destructed, so didn't purge but just blew out the lines with dry air. The center vent temperature was below 40 degrees F (38 if I remember right) in roughly 85 degree weather. Just drive the car occasionaly, but have used the A/C and it still works fine. Do have a problem leaking out refrigerant though. I think those adapter fittings for the fill connections are crap, and may cause a leak depending on which kind you get.

A working aux fan is a must, and a larger condensor I'm sure can't hurt. If you put guages on the system, and watch when the fan kicks in, The high side pressure really drops a lot. Getting rid of that heat is important for efficiency. Now that I think about it, I wonder if making the fan go on all the time when the A/C kicks in rather than based on high side temperature, or adding a larger fan, would improve the cold air output.

I've had very good luck with conversions, other than having a hard time keeping the systems full. As you said, if it is done correctly, R-134a should work about as well as R-12.

A note on the hoses. If you replace them, make sure they are rated for R-134a. If not, I doubt they will stop any leaks. I read an article or two where experts say that older hoses actually reduce leaks since any pores have been filled with oil and plugged over time. Don't know if there is any truth to that.

P.S. Others have stated that the R-134a systems have higher pressures. My experience has seen lower pressures on both high and low sides than with R-12. I don't know if it's due to the specific systems I have retrofitted, or if this is a general rule. Maybe others with higher pressures are using too much refrigerant.

ah-kay · #13 07-14-2009, 02:42 PM

[QUOTE=KCM;2246859]
I've had very good luck with conversions, other than having a hard time keeping the systems full. As you said, if it is done correctly, R-134a should work about as well as R-12.
QUOTE]

x2.

I am a cheapskate, I normally just change out the rec/drier, purge the line with compressed air, check for leak, vacuum the system and recharge with R134a. It always works for me with good results. I do not know what the temp would be like with R12 as none of my cars had working A/C when I bought them.

#14 07-14-2009, 06:56 PM

In the nineties I would convert an R12 system to R134a at the drop of a hat. Things change and so has my thinking. Unfortunately Daves experience is much more common than is a converted system lasting for a number of years.

For me, the irony is that now that I strongly resist moving away from R12, I have the equipment and the experience to do pretty good conversions. The key is charging by weight and starting with 70% of the R12 capacity. From there go up in one ounce increments (virtually impossible to accomplish without a charging scale.) This has to be done with a HIGH FLOW fan simulating ram air through the condensor and the engine revving about 1,500 to 2,000 RPM after about five minutes of this for pressure stabilization. When you see any sign of high side pressure escalation, stop adding those one ounce shots.

Since I started using this procedure I've found no system that will take more than about 76% of it's R12 volume in 134, and these systems seem to perform BETTER than more heavily charged, converted systems.

If you want hard data to base your R12 to R134 decision, I would encourage to study the archives of Steve Brotherton (Stevebfl.) He has a large independent shop in Gainesville, Florida and has kept detailed records on hundreds of converted systems over the years his findings have been that average life of a properly converted system is 1 1/2 to 2 years.

Facts don't lie. With R12 now going for $20 or $30 a pound, it's a bargain.

leathermang · #15 07-14-2009, 07:28 PM

Larry, What do you think about JimmyL's statement about FREEZE12 ?
Or Envirosafe ?

Quote:

Originally Posted by JimmyL

Anything you get out of R134a in these cars would be even better with R12 or Freeze12. I've gone through everything within your description, which to your credit is a very thorough rebuild of your AC system.
In 5 examples I've done, 3 with the complete process you describe above, R134a gives you less cooling, and does it slower than R12 or Freeze12. I currently have a W123 with Envirosafe, but it does not appear any better than Freeze12.