Was discussing this issue with my indy, a terrific MBZ and BMW tech. He's super honest and very fair - ALWAYS!
My concern was servicing my R12 system, it works great now but at 31 years of age it could go on the fritz at any moment, right?

HE SAYS he has quite a few conversions, they just switch out the o-rings, install a new reciever-drier, and charge with R134. You don't have to flush them, the oils mix - that was an old wive's tale - and they work fine. If the system has lost charge then all the oil went out with it anyway.

It's like the biodiesel and stock fuel lines - no need to change them either unless they're already more than a couple of years old. They should be changed every couple of years regardless. Besides, you can't buy a Viton cigar hose anyway.

Some of this stuff gets started and everyone just accepts it as gospel. Sure, there are exceptions, and there are component failures that show up when you start tinkering with these systems.

And some shouldn't be working on their own cars either, the poor guy on the other AC thread doesn't even know what a compressor is. :rolleyes:

I use Ester oil which is for sure compatible with mineral oil just be safe. Here is some retrofit reading material I came across during a quick search just to quench my curiousity. Common points of all documents are to replace the drier and that updating the condensor will improve cooling.

http://www.idqusa.com/faqs.php?c=Retrofitting_an_A_C_System&category_id=14&parent_id=14

http://www.autoacsystems.com/_faqs/detail/retrofit.html

http://www.e38.org/pparish/gm-rp.htm

http://www.e38.org/pparish/gen-rp.htm

http://www.e38.org/pparish/ford-rp.htm

http://www.e38.org/pparish/chry-rp.htm

http://www.aa1car.com/library/retrofit.htm

You are right about that. In the mid '90's, I accepted the notion that R-12 would soon be completely unavailable. Fifteen years later, R-12 is still readily available.

I also accepted the idea that R-134a would work acceptably in a W123. It didn't.

Finally, I accepted the notion that converting back to R-12 was the only way to have good a/c. So I did, and I do.

I don't think that anyone who is knowledgeable about a/c systems would agree with that statement. It's a long ways from being true.

Isn't the internet a wonderful thing? Makes us all a bit smarter, eh? :P

The reciever-drier is a must - it's what collects any moisture in the system and once opened up must be replaced. It's loaded with dessicant, right? So once it gets opened to the atmosphere it absorbs moisture and needs to be replaced.

If the system quit because a seal or a hose leaked, then it can be repaired and recharged with either refrigerant, whichever you can easily obtain.

If it quit because the compressor froze, or it ran dry from some other leak, then it has to be replaced. They don't cost that much, seems a new, not rebuilt one, can be bought for a couple of hundred bucks.

Some of the AC shops I think are preying on the ingnorance of the majority, or they're just not that sharp themselves and so only know to throw lots of parts at it and recharge it. That way they don't have to do it over again because something else in the system acts up once it leaves their shop.

KCM,
"I've also read that the variable orifice expansions valves as used in the older Mercedes are actually better for retrofits than a fixed orifice. I have never found a definitely guide on retrofitting systems."

In speaking about those valves you are mixing types of AC systems... very much oranges and apples... that is why you have not found a guide to retrofitting them into our machines... a fixed orifice is typically used with a compressor which runs all the time.. whereas our systems are ' cycling clutch compressors'.. with the Combo ' block' Txvalve... where the expansion valve is combined with what in other systems would be called a suction valve..

I'm in DFW and my 190 is running with 134. No issues. Perfectly comfortable when I drive around in this hell hole of a city.

I have a leaking shrader valve that I have to deal at the next tech session but other than that I am quite happy with the conversion.

Now don't be shy, tell us how you really feel about this city :)

I am so happy with this forum
 

I have a recently overhauled AC. comp/RD/EV w/ 134

I am going to start calling mechs around here to find one willing to convert me back to r12. Its too hot in NC for a 126 with 134.

I really enjoy this forum alot.

Quote:
Originally Posted by cjbrown
If the system has lost charge then all the oil went out with it anyway.


I don't think that anyone who is knowledgeable about a/c systems would agree with that statement. It's a long ways from being true.
Quote

There's has to be some instance where the above is true. I have a VW with R134 where I replaced the condenser and dryer and recharged. The condenser had 3 pinholes under the clamp mounting plate. NO oil came out when I drilled a hole in the dryer. I was curious why so I cut it open and it was totally dry! The desicant and the 2 filters on the in/out side of the desicant was dry with no trace of oil, the inside of the aluminum housing was also totally dry with not a trace of oil.

My guess is the conenser mounting point rubbed through due to vibration and age while the AC was running and the high pressure freon /oil mix totally leaked out. What do the gurus think?

yes, a condenser leak can indeed dump a significant amount of oil out the system.
however, the compressor in your vw has a sump, and it has oil in it I am sure.
it's very surprising that NO oil was in the reciever, but if your system was out of oil it's because the leaking condenser was letting out freon over a long period of time and the P.O. was adding in freon over and over... each time some oil got out.
this could be why your system is not cooling as well as the pressures indicate steve...

OK A/C Guruus....I'm starting from scratch, compressor died, new R/D has Ester oil, did not change expansion valve because I've changed one before on another SD, old sys was 134 on a '81 SD and I want to go back to r12, planning to get my 609 cert. I have 2 SDs to cool down 81 and an 83.

I can do the work, so what do I buy and where do I buy it?

609
 

get your 609 license online take the test pay for test print out license and buy your r12 online . refrigerantsales.com, EPA CERTIFACATION MAINSTREAMING ENGINEERING

Nothing cools like R12 in an R12 system. Coolest refrigerent ever.
Nothing stops like asbestos brake pads. Best braking material ever. Don't try breathing it.
Both will never be made again.

I think for regular AC systems... fixed systems in houses for instance.. there is a tool for replacing that valve WITHOUT having to evacuate the refrigerant... might be worth checking to see if it can be used on your automobile system.

This is true. My home HVAC guy friend has one & offered to replace a faulty Schrader valve on my MBZ. Check with a home HVAC contractor, he might be willing to loan or even change out the valve for you.