Converting from r12 to 134a

[rkevins]

I am working on a 93 Dodge w250, the heater core needs to be changed so the evap will have to also come out. I am also going to change over to 134a, my biggest question is how to change the oil. How do you get the oil out of the compressor and residual in the system. Can I remove the compressor and pore it out then flush the compressor and system and pore oil in the compressor before evacuation.
I understand recovery I have a 608 permit and going to get my 609, I do refrigeration work just not automotive.

 

[Lou's Garage]

Your procedure sounds good. In my experience, use Ester oil as a replacement (it is compatible with either type of system and their lubricants). Since it's compatible with the existing oil, you won't have to be too fastidious about totally removing all the lubricant.

Lou Manglass

 

[carnutdallas]

Do not change it. Go back with R12... it is designed for that system. I run all my classic R12 cars with R12. The best thing in the world is a 134 cross flow condenser using R12. It is fantastic!

Other wise you have to break all the lines, use a AC flush, and should change the O-rings.

An alternative is Enviro-Safe refrigerant. Called a 134 replacement, but it was really a universal refrigerant that you can run in R12. They were forced to change the label, because technically you cannot mix refrigerant per EPA, but the the Enviro-Safe chemically can with R12 oil.

It is so hard to convert, be efficient and properly prevent oil contamination. After 25 years in the industry, I keep R12 in R12 systems and stopped converting. My 1986 Chevy with freeze you out. So will my 1988 RAMCHARGER and other old vehicles. I learned the hard way to stop converting.


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[firebirdparts]

I have never really understood why you wouldn't just leave the mineral oil in there when you add the new. It can't hurt anything that I can think of. It's a lubricant.

I am a chemical engineer, so I understand why they think they need to use another oil with 134A. But I also understand why that wouldn't cause the mineral oil to "hurt" anything.

I just mention that because 10 guys who are not chemical engineers are going to tell you that 134A and mineral oil are "chemically incompatible" but that is not true. What they are is immiscible. They simply avoid each other.

So anyway, I say don't overdo it. Low effort, low expectations. If it works, you'll just be pleasantly surprised. Put a new drier on it.

 

[MattT]

I have never really understood why you wouldn't just leave the mineral oil in there when you add the new. It can't hurt anything that I can think of. It's a lubricant.

I am a chemical engineer, so I understand why they think they need to use another oil with 134A. But I also understand why that wouldn't cause the mineral oil to "hurt" anything.

I just mention that because 10 guys who are not chemical engineers are going to tell you that 134A and mineral oil are "chemically incompatible" but that is not true. What they are is immiscible. They simply avoid each other.

Immiscibility is the problem. Oil is carried out of the compressor outlet into the system and because the mineral oil is immiscible with R134A it settles out instead of mixing with the refrigerant and returning to the compressor.

 

[like2wheel]

I thought conversions used ester oil that didn't require flushing to remove all the mineral oil?
In fact I seem to remember that it was better to NOT flush the hoses, because the R134 molecules were small enough to permeate the non-barrier hose, & the residual mineral oil helped seal them.

However I do believe that pag oil lubicrates better than ester oil

 

[Fix Until Broke]

Another vote for DO NOT convert to R134a. I converted several systems in the late 90's and they don't cool as well as the R12 unless the R12 system was way oversized to begin with (unusual).

Not sure if a product called "Autofrost" is still available or not, (looks like it is http://refrigerantsinc.com/autofrost.html) but it's an R12 replacement that is "chemically compatible" and has the same boiling points as R12. This didn't come out until the early/mid 2000's and works just as well as R12 without having to convert to R134a.

Just to be clear a system designed to run R134a isn't bad, but it needs more evaporator and condenser area, compressor flow, etc to get the same thermodynamic performance as an R12 system. Newer vehicles designed to run with R134a are good, so there's nothing inherently bad about the refrigerant, just that retrofitting it in a system not designed for it involves some compromises.

 

[VocaTexas]

I've got two pick-ups with the old York compressors on them that I converted to R-134a years ago. All I did was top the compressor with the original type oil and dump 134 on top of what R-12 was left in the system. No problems after all these years and both still blow nice and cold.

 

[Iroc-Z]

I have always changed out the dryer and service ports. Then vacuum and go. Never had an issue beyond that. I figure I am doing more then the diy guys do with just pumping cans in the system

 

[exranger06]

I converted my 92 Accord about 7 years ago, after a bunch of guys on a forum told me not to. I'm glad I didn't listen to them. I still get 42 degree vent temps on an 80 degree day. I can easily buy cheap refrigerant at any parts store, and I don't need any tools specifically for R12. I used Ester oil. I removed the compressor and drained as much oil as I could and reinstalled. I didn't flush anything. I replaced the drier, and most of the o-rings. I didn't bother replacing the difficult to access ones.

 

[carnutdallas]

I converted my 92 Accord about 7 years ago, after a bunch of guys on a forum told me not to. I'm glad I didn't listen to them. I still get 42 degree vent temps on an 80 degree day. I can easily buy cheap refrigerant at any parts store, and I don't need any tools specifically for R12. I used Ester oil. I removed the compressor and drained as much oil as I could and reinstalled. I didn't flush anything. I replaced the drier, and most of the o-rings. I didn't bother replacing the difficult to access ones.

Yep you are correct. You can do it that way, but it does not always work out that well and a GM or Dodge truck is not a Honda, not by a long shot. Pretty sure Honda is a cross flow condenser which helps a ton. Way more efficient and they have some unique features for compressor operation in the early 90’s. Kind of a pain but makes it work well when no electrical fan or relay issues.

Yes the EPA can jack your world up, but the R12 Enviromental issue is a huge scam. DuPont lost the patent, time to create a new business opportunity. If you are a commercial AC operation then venting Freon daily into atmosphere may not be wise. But if it is so terrible, then not a signal R12 car should be on the road and subject to Freon release from a front end collision. They all “seep” anyway. All systems lose, all!!! Most large, tall older buildings use R12. Had a guy come by our shop and try to sell it. He siphoned off the system. We have tester and it was R12, but when we learned how he got it, we said hell no.

So R12 is way more efficient a cooling product. Propane is bada$$ but not safe. Cars designed for it and using it will cool better, especially old, cars and designs that were based on 70’s and 80’s technology. We all have opinions, but 25 years in the business, licensed and carrying an R12 card gives me some first hand knowledge. Any book worm with a degree will always be smarter between the ears but not always practical or knowledgeable in the application.


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[jsaw]

I have converted a lot of systems from R12 to R134, I used ester oil. Never any problem.

 

[ScottsGT]

Subscribing to this one. I recently bought a 1990 F-250 that the guy said the system will work, but "needs a yearly recharge". Trying to figure out which direction to go in.

 

[redmondjp]

Subscribing to this one. I recently bought a 1990 F-250 that the guy said the system will work, but "needs a yearly recharge". Trying to figure out which direction to go in.

Well first, you need to find your leak - look for oily residue at every connection in your system, for starters. That often will tell you where the leak is.

I have a 1990 F350 that somebody did the quick-n-dirty conversion on (screwed the quick-coupler adapters onto the original R12 low and high-side fittings and filled with R134A). I don't think that they changed the oil, and I suspect that my orifice tube is now plugged.

Go over to the ford truck forums (https://www.ford-trucks.com/forums/) and you will find everything you need to know about this topic if you search.

There are two different colors of the plastic orifice tube - blue and red (can't remember, one is for R12 and one for R134A). At a minimum, you need to use the correct one. Then there is the oil issue and I concur with using the ester oil above. I think on my system somebody used PAG oil (which all modern cars now use) which turns into sludge when mixed with the mineral oil originally in the system.

As noted above, you will get slightly less efficiency with the R134A. If you really want to go whole-hog, you can go out to the boneyard and scavenge the components off of a mid-1990s Fx50 truck that used R134A from the factory. I'm not going to do that because I don't want to do that much work.

 

[ScottsGT]

Thanks! But as cheap as parts are on Rock Auto, not worth my time chasing used parts that may be bad. I'll look into the mid '90's stuff. RA has a '95 condenser for $60. Not too bad in my book. About $125 for the compressor, Evap core at $55. Dryer at $15. And I don't have to disassemble a truck twice.
I just need to research this closer now!

 

[CoogarXR]

Last time I had to do an R12 car, I bought some "synthetic R12" from ebay. It worked great. I think I still have a can in the garage. If you are interested, I can go see what it was called.

 

[38Chevy454]

It's best to flush the old mineral out if you convert. Simple solvent flush with mineral spirits or really almost any solvent can work that will help dissolve the mineral oil used in the R-12 system. Then blow air through to clean it out. You can buy special flush aerosol cans, but you can do the cheap solvent flush. Since R-134a is not miscible with mineral oil, any residual mineral oil is just a contaminant on the system that does not add to the cooling.

As stated, the real key to make R-134a work best is you need a more efficient condenser than the old R-12 required. R-134a are commonly called cross flow or parallel flow type. Old R-12 were typically the serpentine type. While the serp type can work with R-134a, it is usually not going to provide best cold air results. Use ester oil (also might be called POE) instead of PAG oil.

Beyond that, once system is blown out and dry, seal it up with new O-rings if applicable, use oil to lube the O-rings to prevent damage. Put required amount of ester oil distributed into the system at various points, especially into the compressor. Pull vacuum and check for leaking down. If good, charge with R-134a and monitor pressures on both low and high sides. R-134a conversions sometimes work best with slight undercharge, but monitoring vent temps will help you determine the exact best charge level.

One caution about the supposed R-12 alternatives. While they may work, many (most) are blends that will work until they leak out and you end up with different mix ratio of the blended refrigerants. R-134a is one component and so even if a small leak over time, recharging is easy and no concern about blended mixes.

 

[wildbill23c]

With my 1988 Ford Bronco 2 AC conversion it was pretty easy since the compressor needed replaced and so did all the o-rings, orifice tube, and accumulator. I just tore the system apart, filled the new compressor with ester oil to the level that was recommended flushed the whole system out then started reassembling everything adding ester oil as required by the service manual to each component replacing all the o-rings as I went. Once the system was back together I vacuumed it down, added leak detection dye and R134A...that was 2 years ago, system is still working great, and still maintains close to freezing temps at the vents. Many stories you hear of it not working are due to the many DIYers not doing a proper system evacuation, replacing o-rings, etc. then trying to recharge a system that was leaking in the first place...top that off with using those stupid DIY off the shelf recharge cans and no manifold gauge set to monitor the system properly....so now they've done a 1/2 a** job, still have a leak or multiple leaks, and then have no idea how much refrigerant they've added.

I'll be doing another vehicle here soon when the weather starts cooperating better, and I'll follow the same guidelines I did for my Bronco 2, a very methodical disassembly of the system, o-ring replacements, oil replacements, and component replacements if needed. If you take your time and do it right and use the proper equipment it'll work fine for many years....I found that the biggest issue is trying to rush through the job and not properly sealing the system.

I also have the 608 certificate which I did prior to doing the conversion on my Bronco 2 which wasn't working to begin with and the whole system had been compromised due to several o-rings leaking (yes I played with the system prior with leak detection dye to find out where the leaks were)...I do plan on getting my 609 at some point as well...can never hurt to know this stuff anyhow. My only issue is I hate trying to work on many of these newer vehicles due to the lack of working space and the location of the compressor if one needs replaced, its just a PITA, otherwise I wouldn't mind doing the work for people as a side job.

 

[Wrench97]

We converted the R12 trucks (Mostly Volvo/Whites with a few Macks) to R134 back in the day by recovering, repairing, evac add Ester oil and recharge without any issues.