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R134a to R12 conversion

Started by smokuspollutus, April 14, 2017, 10:00:05 AM

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smokuspollutus

Hello, all. I'm a long time listener but a first time caller on this forum, usually I stick to the other Cadillac forum, but I think this site will likely have more experience in this area.

I am looking to switch my 1984 Eldorado from R134a back to R12. It was converted prior to my ownership in 2004 and while it will cool the car acceptably while not in traffic or on not so severely hot/humid days (not that either of those two things happen during the summer in NYC), its definitely not functioning up to what I remember the R12 E bodies would do back when they were in daily service over here. I have tried everything that’s been suggested, from cleaning the condenser, evacuating and charging with 80% of the stated R12 capacity, then 90%, then overcharging, and finally back to the 3.5 lbs it was originally converted with (3.5 lbs is the full R12 capacity). Nothing seems to really help. The system is leak-free and the electronic/vacuum facets work exactly as designed, as does the fan clutch and idle controller.

From what I gather, I will need to evacuate the system, replace the drier/orifice tube/etc, flush the condenser, lines, and evaporator, put new seals (I will also be changing the compressor, which was replaced in the early 90s. It seems fine, but I’d like to put off spewing R4 guts throughout the freshly converted R12 system for as long as possible), remove the R134a fittings, vacuum it to check for leaks, and then charge with R12.

Despite distrusting mek-a-niks with care of my Cadillac, I was considering farming this job out until I realized about as many shops still work on R12 as have timing lights. So, here’s my real question, is this possible for someone with a factory service manual, love for their car, reasonable mechanical aptitude, gauges/crow foot wrenches/etc., and no HVAC experience outside of replacing a blend door motor, to do this with any success? I intend to be responsible as far as not venting any refrigerant into the atmosphere as I live here too. So a shop that I have a good relationship with will be recovering the 134a and then vacuuming prior to my charging with R12 to insure what went in comes out, and what goes in stays there. Will I need a new high pressure hose? The 134a fitting is screwed on top of the original port, does simply unscrew and leave the R12 schrader valve intact? What do you use to/how do you flush? Any oil preferred over the mineral oil stated on the sticker?

Thanks for any tips/suggestions you can provide!

Anthony

TJ Hopland

Sounds like you have a decent plan.   

Do you have a vac pump and a gauge set for R12?   Vacuum pump is usually the more expensive tool, even cheap ones are like $150.  Good ones are more $300-500 range.  The vacuum pump uses the same fittings so that  can be used for either system.  Some of the gauge sets can be adapted between the 2 systems but its not recommended because you could end up mixing things.   Back in the day when both were common most people had 2 sets of gauges.   Cheap gauge sets often have issues with the knobs and valves as well as questionable accuracy and reliability.   A good set like the vac pump can be in the $300 range.    I would not attempt any AC work without a decent dual gauge setup.   Even with the dual gauge there is some guessing going on, with a single its almost all a guess.   The vac pump is required if you are going to charge an empty system yourself.   Don't bother with the air compressor powered vac pumps.  The do work but require so much air from the compressor even an advanced DIY sized compressor can't keep up and forget it if you have say a 30 gallon or smaller semi portable unit. 

On the conversion fittings some of them did require you to remove the original valve core but they are easily replaced.

I have not switched a system back so I don't know if there are special considerations there.  The oil is an interesting question.   If I was doing it I think I would use ester oil which is also what I use in my 134 systems.   PAG and mineral oil really seem to have issues if they get mixed and it seems like even a careful flush can leave some behind.   Ester can work with both systems and doesn't have have as big of issues if it mixes with traces of either mineral or pag oil. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

smokuspollutus

Thanks for the reply TJ. I do not have a vacuum pump but do have R12 manifold gauges. I was under the impression that to charge I don't need a vacuum pump? What I was planning to do was to rebuild the system, then take it to a shop to sit on their vacuum pump overnight to make sure there are no leaks. From there, take the car home and charge it, once there's enough refrigerant just kick the compressor on and have it do the work to suck in the rest. Am I thinking about this the right way? Will I contaminate the shop's vacuum pump even without any R12 in the system?

"Cadillac Kid" Greg Surfas 15364

Anthony
Without belaboring the point the critical thing is to get the system internals "hospital" clean to remove ALL traces or residual oil and debris out before you start to reassemble it. I would suggest Mineral oil since R12 and it are old friends and work well together. 
After assembly the system should be.checked for leaks UNDER PRESSURE.
Sounds like you have the rest of it handled.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

76eldo

I bought a vacuum pump and a set of gauges so that I can do my own AC work on my cars.

The vacuum pump should be connected to the system along with the gauges.  Leave the pump on for a couple of hours and the system should pull down to -19 or so.  Then turn off the pump and let it sit for about an hour.  The vacuum should hold.  If it does not hold then you have a large leak.  You say the system is tight but you also say that you are going to install another compressor so you need to do the leak test under vacuum first.

Greg states to test the system under pressure.  There are cheap and inert gasses like nitrogen available to test the system under pressure but I have never tried to find a can of nitrogen that I can connect to my gauges.

If the vacuum holds then I go to filling the system with Freon R-12 to the recommended level and you should feel cold air coming out of the vents.

Changing the drier and orifice tube is a must and they are the cheapest components in the system anyway.

Flushing out the condenser is also necessary.

The investment in the vacuum pump is a good thing because you can sell it at sometime in the future.  There are always used ones on craig's list.  I got a new one on ebay for about $150 and it came with a set of 134A gauges.

Good luck and stay COOL

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

smokuspollutus

Greg and Brian, thanks. Mineral oil it is. A question here, I see an aerosol style mineral oil "charge" and then straight mineral oil in a bottle. Which do I need? I am going to say the bottle to lube things while its open, but do I need to add an additional amount after I've sealed it up and charged with refrigerant?

Is there a preferred type of flush? I assume there must be some pressure behind the cleaner to force it through the condenser and evaporator. I do have a good relationship with a local shop who's willing to help me out so the leak test will probably be performed by him by whatever means he has access to. If I had more than just one R12 car I would invest in a complete setup, I frequently see R12 machines for sale on craigslist for not too much but I can't justify the space it would take up in my garage for how often I (plan) to use it. I would prefer to do the actual flushing of the system myself just to make sure its done right.

Should I need to change the schrader valve, is it largely the same concept as replacing one on a tire?

Thanks again for the help guys, I've read up on how this stuff basically works but my knowledge stops at theory.

"Cadillac Kid" Greg Surfas 15364

Anthony,
Opinions on what can be used for an effective flush seem to go as the inverse of refrigeration experience.  I have been in the Refrigeration and Air Conditioning industry for over five decades and experience  has shown me this is no place to go cheap.  Anytime I do a thorough flush i use a material obtainable at any refrigeration wholesaler for about$100.00 called RX11.  Your AC shop guy can get it for you and it comes in a kit with instructions.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

smokuspollutus

Thanks Greg. I'll pick some up and keep this thread updated with how this all works out.

30326

Is it legal to switch back to R12? I think its not okay in Europe.

Also found the following information:
http://www.aircondition.com/tech/questions/39/differences-between-r12-and-r134a
Pretty good explanation.


The Tassie Devil(le)

Not legal in Australia, but in America, it seems people can do anything.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

"Cadillac Kid" Greg Surfas 15364

What hole in the Ozone layer?
GregSurfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

The Tassie Devil(le)

I won't get into specifics, but I can walk around without my hat on in 100 degrees in the Northern Hemisphere, but cannot do that down here.

Can't even drive around in my convertible with the top down on a hot day.   The Sun is just too biting.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

TJ Hopland

I think the deal in the USA is we are not allowed to produce or import R-12 and are not allowed to manufacture or sell a complete machine that uses it.   Greg can probably confirm because I would imagine those details are part of the refrigerant handlers license/permit process.  R-12 that was already 'here' when the rule took effect can be sold and we can manufacture and or import repair parts for R-12 machines.    Many people stockpiled R-12 at the time and drove the prices up so high that most of the equipment got replaced or converted so the result was a lot of that stock is still 'in stock'.    Same thing has happened? to R-22 and I assume will happen with R-134a soon.    I have seen new machines in some dealer shops so its got to be 17's or maybe the early 18's that are starting to change over to the next thing. 

I agree good flush is expensive and worth it.   I used some parts store stuff on one system and didn't really see much come out.   I got stuck looking for some parts and ended up at a shop that does a lot of classic cars and I bought a can of what they recommended and did it again and was amazed at what came out with their product.   I don't remember the name but it came in a metal can and $100 for a gallon seems like the right ballpark.   What it seemed to loosen up and remove was the varnish like build up that was inside everything.   Even working outside I had to step away a few times for 'fresh air' so its likely pretty toxic stuff you won't want to get on your skin or on paint. 

The valve cores look and work pretty much like the ones on tires.   I bought an assortment pack at a parts store.   They had a large set that came in a plastic organizer but also had what looked to be the same options in a little 10 pack.   I think it was from one of the major brands like Four Seasons.   The pack had like 3 each of 3 different styles that seem to cover a most of the older stuff.   I can't remember if I used a tire tool or if I have a special AC one.   I bought some sort of tool kit that has an extractor for the orifice tubes and maybe an O ring tool so I am thinking maybe that kit had a core tool too.   

Testing for leaks with vacuum isn't really a good test since the system always works under pressure.   The vacuum can actually hold things together like say a fitting you forgot to tighten.   I think its my 73 that has a part on it from vintage or old air that has a swivel on it that won't hold vacuum, if you shut the pump off it bleeds off in less than an hour.   I called them and complained, they said that seal isn't designed for vacuum so pressure test it or just charge it so that is what I did.   4 years later its still working.

The reason I can't remember any of this stuff (other than age) is I bought all these tools like 4 years ago and fixed all my stuff 'right' and it has worked ever since.    Before I did that it seemed like it was an $800 repair at the shop for at least one rig every summer.   Next summer it was another seal or something else so another $800.      The sign may say AC diagnostics $79 but it always seems to cost at least $800.    $800 is a really good start on tools and supplies.   The first couple cars were likely more of a break even cost wise but after that you are saving money so if you have lots of cars and like AC it could be worth the investment. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

smokuspollutus

Thanks for the replies guys. The EPA certification didn't say anything about a reverse conversion, but I have to say that before that test I could hardly spell refrigerant, and now I be licensed in it! I am going to take all precautions and definitely not vent anything into the atmosphere.

Question on orifice tubes, should I just get the stock replacement or a "performance" part? Is there any difference? I was satisfied with the way these systems operated stock, but if there is room for improvement, I'd be happy to do it. I assume there must be some sort of trade-off? I don't usually leave the NY/NJ/PA area and drive this car mostly in the summertime, hot and soupy most of the time. Lots of city driving/stop and go traffic.

TJ Hopland

In all the reading I have done no one seems to have been able to verify either way that a different or variable orifice really helps.   I think there are just too many other variables in a typical automotive system to really be able to tell.     I think on my Suburban I may have got the one 'they' said was better but I don't remember thinking the performance was anything special.   If it was better than the stock one I suspect a lot of people would have quit buying Suburbans if they lived anywhere warm because it barely worked.   The system didn't work when I bought the truck so maybe the 'better' one was actually worse.   Rest of the system was stock and it was a 96 so it had the system designed for 134 vs the earlier ones that were more or less the r12 systems.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364

Anthony,
The orifice tube is a pressure dependent flow control device.  For your location the standard unit will provide the best flow characteristics.  Going to one calibrated for (typical ratings) say over 100 degrees ambient will actually reduce the flow rate at "your" temperatures.  The purpose of the flow control device in any refrigeration system is to control the flow to match the capacity of the compressor under full load at anticipated suction pressure.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

TJ Hopland

That makes sense.   Average ambient temps is just one of the things 'they' leave out when they say this other valve is 'better'.

Factory just chooses the sized based on what they think is going to be an average?  Would something intended for sale in Canada have a different orifice than say Mexico?  Or don't they put that much effort into it?

Do the variable orifice tubes they sell for these apps work at all?  I was guessing not since the factory apparently didn't use them.   

StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

smokuspollutus

#17
Sounds like stock is where I'll stay then. Thanks guys. Also, opinions on preemptive evaporator replacement? The original was changed in 2004 when the system was converted. It doesn't leak, but what is life expectancy on one of these? Is it likely to be full of crap that needs to be cleaned off it (in which case I'd just replace it anyway). If it is likely to last a long while, or if anyone knows that for some reason the new units are worse than the old, I'm more than content with keeping it and not taking the HVAC box apart.

TJ Hopland

Later 80's and early 90's seemed to be when GM has a lot of short lived evaporator cores.   I don't remember it really being a common issue for the earlier 80's stuff but that was back when I was poor and didn't mind being hot so maybe I just didn't pay attention.  A new cassette deck would have been higher on my list back then.   

The orifice usually does a decent job of keeping big chunks out of the evaporator.   Condenser is what usually catches and retains for a while parts of a previous failed compressor.   The cross flow condensers work well but are darn near impossible to fully flush so if you really want a system to work well and for a long time replacing it is the way to go.   

The cross flow ones are just like a radiator where there are basically tanks on both sides and thin narrow tubes with the fins between the tanks.   The older style you could see one long continuous tube zigzagging though the fins.   That style can be flushed because there are no tiny passages and you can force flow through the entire path.   On the cross flow ones the solvent or refrigerant just takes the path of least resistance, you never really know if some of the passages are blocked by debris or when that debris make get knocked loose and travel further into the system.     To properly clean one you would have to treat it like a radiator and remove the tanks to access the fin tubes that you would then flush individually. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

smokuspollutus

I will probably leave it. With my luck I'd get some kind of imported unit that'd go bad just as soon as its fully charged. Anyone ever notice buildup on the fins themselves (external)? There was precious little buildup on the condenser when I cleaned it, I am going to assume that it'd probably be the same for the evaporator. If anyone can advise otherwise, I'm all ears.