88' 560SL AC conversion question

[slboy]

I have been thinking about 134 conversion for a while. However I am not sure what type of oil used in 560SL. Does anybody know? Will a flush clean out the system? What is best way? change to R134 or stay at R12?

Please help, Thanks!

[SunGuy]

slboy,
If you have no existing leaks and are not losing R12 in the atmosphere, I'd leave it alone and stick with the R12 that's in there. The only other caveat is availability of R12 locally to you. It's not that hard to find, IMO.

Conversion to 134, again IMO, yields little to no benefit, is expensive in parts as you'll need to replace the receiver/dryer, expansion valve + pay for a chemical flush to get the old oil out of the system, plus the fill cost for 134. When you're all through, I don't believe you'll experience any greater degree of cooling and be out a fairly large chunk o' change for your efforts. The nippondenso compressor that you probably have in your car was designed to run on R12.

You've asked a very good question which I'm fairly certain will bring in more than a few opinions/facts to consider. In the meantime, you may want to use the search tool here as this subject has come up a time or two or three...

Bob

[neds380sl]

I've read that the change out of parts is actually unnecessary (search google), and you can simply remove the R12 and install 134 and the system works fine. You can buy a kit to change over the valves, they're a different size. The oils are compatible too, so your compressor should work OK with no problem. Unless you have the vacuum pump, etc., it all needs to be done at a shop. They should buy the R12 from you, it's expensive stuff. All that said, if your system isn't giving you trouble, I'd leave it alone. Ned

[plink49]

Although not an SL, I had my same vintage ('86) 300E converted from R-12 to R-134a 2 years ago and the cost for parts (including the 134) and labor was $250. Just the cost of the R-12 to recharge the old system was almost that much! I must say that the cooling effeciency declined slightly with the conversion, but not all that much not to have it done.

[UT_Tech]

There is one slight advantage to to R134A. Many older cars develop a very slight leak, something on the order of one lb or less per year. Often the condition will stabilize for years. If you have R134A then you can safely top-off the system if you have a gauge set (<$100 at Harbor Freight). Unless you can find a black-market source there's no way to buy a 12oz can of R12. R134 is available plentiful and and cheap at your local parts store. I would prefer to throw in a can per year of refrigerant rather than replace an evaporator in a 140 chassis.

[JPMOSE]

My 560SL was converted to 134a two years ago and really don't have any complaints. Furthermore, I did not have to change out any parts other than the dryer and fittings. I get 40 degrees F from my center registers. One of only drawbacks is the time it takes for the air to start blowing out cold. With R12, it only took seconds before you'd feel cool air. With 134a, it takes around 45 seconds before it really starts to cool and up to 3 minutes for good performance. Beyond that, I have not complaints.

I agree with Steve....it is nice to be able to legally top off the system if it has a very slow leak (quite common in older cars).

[slboy]

Many Thanks to you all SL guys:

Yes I have to agree with UT_tech that you can safely top off the system. I have been heard about different opinions on conversion. People will tell you you need to change parts and some will disagree. Actually I did the the R134 conversion on my 86 4 Runner by simply changing the fittings, vaccum pumping the system and charge R134 directly. It works fine so far.

However I have read that there are two types of oil used by R12 system. Only one will well with R134. So my questions:

1. What kind of oil is in SL system;
2. Can two oil mix together?
3. Where can I find some R12 in Dallas area (sensitve question I guess)

Thanks!!!!

[ScottinSoCal]

Originally Posted by slboy

1. What kind of oil is in SL system;
2. Can two oil mix together?

Sorry, no help on 3.

1. The R12 systems (all of them, not just the 107) used mineral oil as the lubricant. R134 uses synthetic oil, like PAG. You should NOT use mineral oil with R134, it'll ruin your system over time.
2. Absolutely not. Your system has to be flushed and cleaned to convert from R12 to R134.

[slboy]

Alright I will consider a flush before my conversion. It should be easy since my system is empty now I guess. I kown AutoZone have some AC flush solvent. But you have to take apart the system and flush individual components some thing like. Does the AC shop do it different?

Any suggestion???????? THANKS

[lystgl]

I may be too late in responding but there is an R12 like refrigerant called "Duracool" that requires no part changing at all and is fully compatible with R12. It's enviro friendly and easier on the system than either R12 or 134.
http://www.coolearthinc.com/
A six oz can of Duracool is the same as a 17 oz R12 equivalent though it operates at the same pressure/temperature as R12
I haven't used it in my 560SL as it works fine as is but I have used it in my daughter's Chev Silverado 1990 and it works perfectly.

[Graham]

Originally Posted by slboy

Alright I will consider a flush before my conversion. It should be easy since my system is empty now I guess. I kown AutoZone have some AC flush solvent. But you have to take apart the system and flush individual components some thing like. Does the AC shop do it different?

Any suggestion???????? THANKS

I would flush everything I could especially if a compressor has died.

One thing when recharging with R134a, make sure you do not over-charge it - It should have about 85-90 % of the weight of R12 recommended for your car. So, if your car needs 1kg or 2.205lb, then use 1.9 to 2.0 lbs of R134a. And use the proper ester oil.