R134a and R4 - PeachParts Mercedes-Benz Forum

cbjukraine · #1 06-24-2012, 10:51 PM

It's summer, it's hot, and A/C threads abound... here's another one.

What is it about R134a and the R4 compressor not seeming to get along? I've put two compressors on my car in less than a year, and I'm about to put on another (CompressorWorks this time). I don't want to keep doing this, so what should I do?

Here's my list of questions:

1) If I install a parallel flow condenser, will that help extend the life of the compressor?
2) Are there any other components that need to be added or changed when adding a parallel flow condenser?
3) After flushing the whole system, what type of oil should I use? And how much oil?
4) What should I use to flush? I've heard acetone, mineral spirits, expensive flush solvent with gun...
5) If I wanted to go back to R12, what has to be changed? Do I need to replace all the o-rings? How do you know you've flushed all the PAG oil out?

Sorry for all the questions, but thanks!

Graplr · #2 06-24-2012, 11:10 PM

1- Yes
2- Yes, you will need to fabricate new hoses (or have a shop do it) as the connections will be different sizes (at least one will) and in a different location. You can buy your own crimper for about $150.
3-Ester oil is the common oil used in R12 convert systems.
4-This is more opinion than fact.
5-R12 does not need the barrier hose and green orings so no you don't need to change them if going back to r12. If you do a good flushing, you should get all the oil out. Flush the compressor with the new oil that you will be using.

vstech · #3 06-24-2012, 11:48 PM

a direct bolt in kit for PF condensers for the 123 are available I'm not sure where I saw the kit, but it's listed on here somewhere.

Air&Road · #4 06-25-2012, 08:46 AM

First of all, the obvious solution would seem to be to use R12.

Beyond that, if you decide to go to a PF condensor, be advised, that if it ever becomes necessary to flush a PF condensor it is almost impossible to do so. IMHO, they are not the Panacea that some people would lead you to believe.

Graplr · #5 06-25-2012, 11:41 AM

Quote:

Originally Posted by vstech

a direct bolt in kit for PF condensers for the 123 are available I'm not sure where I saw the kit, but it's listed on here somewhere.

I think I saw one on fleebay. I believe it came with new hoses. IIRC it was around $250-300.

Edit- Just found it. Looks like it is no longer for sale. Perhaps contacting the seller would help.

Mercedes W123 Parallel-Flow Condenser Conversion Kit (240D, 300D,TD,CD) | eBay

As Larry stated, converting back to R12 may be the simplest method for you (assuming you can get some R12 of fleebay or Craigslist).

Brian Carlton · #6 06-25-2012, 11:47 AM

Quote:

Originally Posted by Air&Road

Beyond that, if you decide to go to a PF condensor, be advised, that if it ever becomes necessary to flush a PF condensor it is almost impossible to do so. IMHO, they are not the Panacea that some people would lead you to believe.

I agree with this.

Didn't Dave install the PF condenser with little benefits to show for it? Using R-12 with the existing condenser and a properly operating auxiliary fan should be satisfactory up to about 100F.

Of course, down in Dallas, you might need to get the limited additional benefits from the PF condenser due to the extreme heat.

I might consider heavily tinted window glass in lieu of the PF condenser............reduce the heat load and you don't need the cooling capability.

Graplr · #7 06-25-2012, 12:46 PM

Quote:

Originally Posted by Brian Carlton

I agree with this.

Didn't Dave install the PF condenser with little benefits to show for it? Using R-12 with the existing condenser and a properly operating auxiliary fan should be satisfactory up to about 100F.

Of course, down in Dallas, you might need to get the limited additional benefits from the PF condenser due to the extreme heat.

I might consider heavily tinted window glass in lieu of the PF condenser............reduce the heat load and you don't need the cooling capability.

I put a PFC in my 84 SD. I started with R134a in it and got vent temps at about 45 degrees IIRC during MN summers at highway speeds (Temps up to 90F). Then I decided to put R12 in (I used ester oil so I just took the R134a out and put R12 in). I noticed only a few degrees cooler with R12 at vent temps. There are a lot of variables and I was hardly scientific but it is something to compare to.

Brian Carlton · #8 06-25-2012, 12:53 PM

Quote:

Originally Posted by Graplr

I put a PFC in my 84 SD. I started with R134a in it and got vent temps at about 45 degrees IIRC during MN summers at highway speeds (Temps up to 90F). Then I decided to put R12 in (I used ester oil so I just took the R134a out and put R12 in). I noticed only a few degrees cooler with R12 at vent temps. There are a lot of variables and I was hardly scientific but it is something to compare to.

I had the SD out recently (also an '84) and also at 90F. The vent temp was 50F. at high blower speed...........dropping to about 43F at low blower speed, at which point the compressor would cycle.

This is with R-134a.

The PFC might garner two or three more degrees and the R-12 might garner another five degrees. However, once the compressor begins cycling, the benefits of the PFC or R-12 are eliminated. The system attained the minimum evaporator temperature allowed by the ETS.

For those in brutal climates, where every degree matters, the expense of the PFC and, possibly R-12 is worthwhile. For everyone else, it's overkill.

If I need to rebuild the system on the SD, I'd go with R-12 (which I now have), but I would not make the effort to do a PFC.

Air&Road · #9 06-25-2012, 01:52 PM

Yes, there's a lot to be said for window tint, ESPECIALLY if the car has to set in the direct sunshine and heat soak all day.

There are several places in our parking lot that are in really good shade. I usually get in early enough for one of these places. On a 95 degree day, in the shade, when I get in the car, the thermometer is not much above 100 degrees. If left in the Sun all day the vent thermometer shows 140 when I get in.

I would expect window tint would bring that 140 down noticably, and of course the real test, would bring down the heat load even after cooled off inside. I've been dragging my feet checking on window tint because if you use the film, it's a one way road. Taking it off the back glass if it gets in bad shape is impossible without ruining the defogger.

1980sd · #10 06-25-2012, 02:28 PM

I 2nd the window tint. My AC is working about as good as it gets yet I notice sun coming through the windows warms surfaces up QUICKLY once I get out of the shade.

ohio diesel fan · #11 06-25-2012, 03:21 PM

i've been wondering about this as well. saturday while out with the wife my a/c stopped blowing cold and i could hear a faint whining. since this will be her main mode of transportation a/c is imperative. i went through all the service records, and it appears to have been converted to 134, but it still has the r12 sticker on the radiator support. would my best course of action be to bite the bullet and take it in to a shop?

Air&Road · #12 06-25-2012, 03:26 PM

Ohio,

Unfortunately, it sounds as if your car is one of the millions that have seen some rogue conversions. By law, fittings specific to the refrigeration in the system as well as labels are SUPPOSED to be installed, but too many system gets converted to any and all refrigerants without labels or fittings.

If you wish to approach the problem yourself, it would be best to take it to an auto a/c shope first and ask them to identify the refrigerant. They will have an instrument called a Refrigerant Identifier and will be able to determine if it is a legitimate refrigerant and you will then be armed with enough knowledge to know which direction to turn.

Post the results here and we will try to help you through it.

cbjukraine · #13 06-25-2012, 05:04 PM

So there's nothing about the R4 compressor that doesn't work well with R134a?

Is it just that the R4 is a marginal compressor in terms of durability/reliability no matter what refrigerant you're using?

Graplr · #14 06-25-2012, 05:45 PM

Quote:

Originally Posted by cbjukraine

So there's nothing about the R4 compressor that doesn't work well with R134a?

Is it just that the R4 is a marginal compressor in terms of durability/reliability no matter what refrigerant you're using?

R134a runs higher pressures than R12 so the compressor life expectancy on r134a will be shorter but three in one year is excessive. Are you replacing the dryer and flushing the system? You could have contaminants that are taking out the compressor.

Graplr · #15 06-25-2012, 05:51 PM

Quote:

Originally Posted by ohio diesel fan

i've been wondering about this as well. saturday while out with the wife my a/c stopped blowing cold and i could hear a faint whining. since this will be her main mode of transportation a/c is imperative. i went through all the service records, and it appears to have been converted to 134, but it still has the r12 sticker on the radiator support. would my best course of action be to bite the bullet and take it in to a shop?

Check which ports are on the lines. R12 are smaller and have threads where r134a look like cylinders with mo threads. No one fakes the old r12 sticker off they just put a new sticker on. Often times these stickers fall off. I would say it is very likely you have r134a in the system.

If your ac is not working it is probably low or out of refrigerant so it is probably a moot point as to what is in it unless you just want to top it off.