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How did R134a converted systems work

Started by "Cadillac Kid" Greg Surfas 15364, July 27, 2021, 07:29:19 PM

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"Cadillac Kid" Greg Surfas 15364

Just wondering how those folks in the areas of the country experiencing unusual ultra hot weather are finding their AC systems that have been "converted" to R-134a are working?
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-

hornetball

Mine is doing OK.  Not as cold as R-12 (obviously), but still quite cold (similar to my newer cars).

scotth3886

#2
Quote from: "Cadillac Kid"  Greg Surfas 15364 on July 27, 2021, 07:29:19 PM
Just wondering how those folks in the areas of the country experiencing unusual ultra hot weather are finding their AC systems that have been "converted" to R-134a are working?
Greg Surfas

Not unusually hot here, but high 80s low 90s and humid.  Changed back to R12 last summer and that helped, but still the blend door vacuum pan needs replaced.  I won't really know until that's done.

The Tassie Devil(le)

G'day Greg,

Mine is doing okay.   When it was charged up, (in 2008) we used a thermometer at the dash outlet, and if I remember correctly, it read 32 F or 33 F.

In 2012, up in Queensland, I thought it was not working quite as well, and had it checked, but it was still good.   Just that the heat and humidity in Queensland was unbearable at the time.

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

Scot Minesinger

Greg, I'm in VA and only run the ac when I cannot drop the top, which is when it is raining.  The ac works awesome for that purpose.  Temperatures are mid 90's and humid, then if it rains in the evening or afternoon it is in the 80's and 100%RH.  If I owned a closed car, might be different.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Eric DeVirgilis CLC# 8621

Not great on an '87 Town Car that was converted long before I got it. Seems to work okay below 85 deg but 90s and above not so good. I have yet to see a quicky-conversion perform as well an original R12 system.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

EAM 17806

GREG:  On my 76 Coupe Devile it's working quite well and I am satisfied.  EAM
Ev Marabian

1976 Cadillac Coupe DeVille, 1989 Chevrolet Caprice Classic, 1990 Pontiac Bonneville and 1996 Buick Skylark

Cadillac Jack 82


My system is still an R-12 system and it seems to work well even if its 110 degrees.  It takes a while to cool the cabin but when it does it's quite comfortable.
Tim

CLC Member #30850

1959 Cadillac CDV "Shelley"
1964 Cadillac SDV "Rosalie"
1966 Oldsmobile Toronado "Sienna"

Past Cars

1937 LaSalle Cpe
1940 Chevrolet Cpe
1941 Ford 11Y
1954 Buick 48D
1955 Cadillac CDV
1955 Packard Clipper
1957 Cadillac Series 62
1962 VW Bug
1962 Dodge 880
1966 Mercury Montclair
1967 Buick Wildcat Convertible
1968 Chevy Chevelle SS
1968 Plymouth Barracuda
1977 Lincoln MKV

smokuspollutus

Question here. We all know that some hit in performance is taken with a 134 conversion. Largely due to the R12 tube and fin condenser that isn't as efficient as a 134 spec condenser that looks like a radiator, like we find in cars today.

Here's a question, what would be the effect to add a "better" 134a condenser into an otherwise R12 system? I assume there must be some kind of gotchya or some OEM would have done this at some point.

MaR

The main issue is the orifice valve (or whatever the equivalent in the system is). It's not "tuned" properly for the R134A refrigerant so the system is not letting the evaporation and condensing cycle happen at the proper (most efficient) pressures.

"Cadillac Kid" Greg Surfas 15364

Didn't mean for this thread to go off this way as I was just curious as to the effect that these unusually hot conditions have affected "converted" systems in those areas not used to the heat.
As far as the technical aspect of R-134a vs. 12, as I stated earlier, the SOLE reason for the decrease in capacity in an otherwise unaltered system is the compressor.. Refrigerants have a pressure at which they will condense for any given temperature. At a condensing temperature of 140 degrees (the ambient plus 40 which is typical for automotive systems, R-12 would be 206.6 degrees F. and 134a would be 230.8 degrees F.  Divide those condensing temperatures by the evaporating pressure at 35 degrees (32 for 12, 25.6 for 134a) gives you the compression ratio which is 6.45 for 12 and 9. 1 for 134a.  The difference is just about 40% which results in a decrease of performance (OF AN UNALTERED A6 COMPRESSOR) of just over 20%. Of curse for maximum performance ALL the system's components should be correctly sized for the refrigerant intended to be used.
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-

Cadman-iac

#11
   Greg,
  I live in Southern Arizona and have 2 of the square body Suburbans that I converted to R134A, a 90 and an 88, both have dual air with the R4 compressors, and I went through both systems with all the necessary parts replaced, including the condensers.
It's been extremely hot here this year, and now it's also very humid due to the monsoon season. Given that the cabin area is almost the largest of any vehicle made, these are working pretty good. Granted they are not as good as they were when they had R12, but they will still have to be turned down once the interior has cooled, or they will freeze you out. I was pleasantly surprised by that.
The 88 needs to be topped off now though because it seeps around one of the fittings, but that's not a problem.

On a side note, I'd like to add that I had problems previously with the first conversion I did because I had used the regular oil recommended for R134A, and I had compressor issues.
The second time around, I used the synthetic R134A oil and have had absolutely no problems with either one after over 2 years now. The first one lasted for just over one year before the compressor got really noisy and started to grenade.
The new condensers I think are the new design, but I'm not positive about this. I'd have to find the old ones and compare them to know for sure.

  If I had the R12 to do it, I would have left them that way, but since I didn't, they got converted. I don't regret it now, but after the first one crapped out I had my doubts. The synthetic oil is crucial in the conversion though. The regular oil just doesn't seem to be carried through the system like it should be. At least that's my experience, what have others had?

Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

Quote from: "Cadillac Kid"  Greg Surfas 15364 on July 28, 2021, 12:59:05 PM
Didn't mean for this thread to go off this way as I was just curious as to the effect that these unusually hot conditions have affected "converted" systems in those areas not used to the heat.
As far as the technical aspect of R-134a vs. 12, as I stated earlier, the SOLE reason for the decrease in capacity in an otherwise unaltered system is the compressor.. Refrigerants have a pressure at which they will condense for any given temperature. At a condensing temperature of 140 degrees (the ambient plus 40 which is typical for automotive systems, R-12 would be 206.6 degrees F. and 134a would be 230.8 degrees F.  Divide those condensing temperatures by the evaporating pressure at 35 degrees (32 for 12, 25.6 for 134a) gives you the compression ratio which is 6.45 for 12 and 9. 1 for 134a.  The difference is just about 40% which results in a decrease of performance (OF AN UNALTERED A6 COMPRESSOR) of just over 20%. Of curse for maximum performance ALL the system's components should be correctly sized for the refrigerant intended to be used.
Greg Surfas

    So how well would an A6 compressor actually work if you used R134A in it without changing anything except for the oil?
I have an under-dash unit that I am thinking of using with an A6 compressor and an R134A design condenser. Do you think it would work well enough, or would it be necessary to modify the compressor?
And what modifications are required for an A6 if you were wanting to go with R134A?
Thanks for any advice you can offer.

Rick
 
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadillac Jack 82


Rick if you're close to Scottsdale I'd recommend Legends Luxury Auto.  Danny is a wizard with anything GM.  He also seems to have a good supply of R12 if you ever choose to convert your cars back to R12.
Tim

CLC Member #30850

1959 Cadillac CDV "Shelley"
1964 Cadillac SDV "Rosalie"
1966 Oldsmobile Toronado "Sienna"

Past Cars

1937 LaSalle Cpe
1940 Chevrolet Cpe
1941 Ford 11Y
1954 Buick 48D
1955 Cadillac CDV
1955 Packard Clipper
1957 Cadillac Series 62
1962 VW Bug
1962 Dodge 880
1966 Mercury Montclair
1967 Buick Wildcat Convertible
1968 Chevy Chevelle SS
1968 Plymouth Barracuda
1977 Lincoln MKV

Cadman-iac

Quote from: 55 CDV Fan 82 on July 28, 2021, 02:31:57 PM
Rick if you're close to Scottsdale I'd recommend Legends Luxury Auto.  Danny is a wizard with anything GM.  He also seems to have a good supply of R12 if you ever choose to convert your cars back to R12.

  Thank you Tim, that's very good to know. You don't happen to know what the going rate is for R12 right now would you?

  Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

scotth3886

I pay about $40 per 12 or 14oz can.  I have an unused 30lb tank so anytime I need any I use the same brand in cans versus opening up the tank.

"Cadillac Kid" Greg Surfas 15364

Rick,
As I said above, the "hit" for using R-134a in an un modified A-6 compressor is about 20% capacity reduction. Now this may not be felt during highway operation, but is painfully obvious during low speed excursions in heavy traffic.
As far as modifications to the A-6 to overcome the loss of efficiency the "trick" is to make it more efficient and that goes back to using old hot rod tricks. I modified the cylinder block to reduce the clearance volume (space when the pistons are at the top of their travel, enlarged the transfer ports and, probably the most important, had valve plates and valves modified to increase flow.  Not really sophisticated, but effective.  I got R-12 performance out of the A-6 in my 66 CdV.  Oh, by the way, the cost was somewhat north of 3k to have valve plates and valves made.  It worked, but I would not consider that cost effective.  Perhaps when all we can get is HFO-1234yf which is the current refrigerant Cadillac is using in all its new cars, which when used in R-134a systems results in a drop of about 18% (read that a total reduction of capacity for an R-12 system of near 40%) costs will take a back seat to function.
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-

Bill Balkie 24172

#17
Hello ,
    Bruce mentioned a few post back that his temperature at the vent was  32 or 35°.   My vent out temperature is about 45 and the inside of the car is very comfortable. Does any body else have vent Temperatures that they can chime in on?  Maybe my thermometer is off?
    Thanks,
          Bill
Bill Balkie
1970 Coupe DeVille
2009 CTS

marty55cdv

   Vent temperature in my 59 Fleetwood with a A6 conversion is 42 while moving, drove this car on the day SLC had its highest recorded temp of 107 degrees last month, I had three passengers and was in traffic most of the time, the temp in the car was bearable but not chilly by any stretch.   My 60 Flattop same setup,  is usually around 40 Degrees at the vents. 
Marty Smith
  CLC #22760
41 60 Special http://bit.ly/1Wm0GvT
55 CDV http://bit.ly/1G933IY
56 Fleetwood
1958 Extended Deck http://bit.ly/1NPYhGC
1959 Fleetwood  http://bit.ly/1OFsrOE
1960 Series 62 Coupe
1960 Sedan DeVille  4 window Flattop
63 Fleetwood http://bit.ly/1iSz17J
1964 Eldorado http://bit.ly/1Wm17GA  (Living in California now)
1988 EBC http://bit.ly/1iSACKz

"Cadillac Kid" Greg Surfas 15364

If I may, another simplistic explanation of "capacity".  The A-6 compressor is rated at 27,000 BTU's at 2000 (compressor) RPM. It turns at 1.48 times the engine speed.  That means that at about 50 MPH with the engine turning over at 1500 RPM the AC system is operating at full (27,000 BTUH) capacity.
Now the heat load on the car is constant regardless of it's speed, and that 27,000 BTUH is the calculated maximum cooling load (as was determined a billion years ago in actual testing).
Here comes the problem with reducing the capacity of the A-6 by switching to R-134a and loosing 20% of it's capacity.
When you are in traffic, say stopped with the engine idling. Now the engine speed is below 500 RPM and the compressor is turning at about 750 RPM.  With the cooling load still high, the capacity with R-12 is reduced to something like 10,000 BTUH (with R-12) or 8,000 with R-134a.
Vent temperature is dependent upon the system type, the out door temperature and the out door humidity. "Ice cold" is not necessarily good, since cold air drops and very cold air drops further, pooling in the lower half of the car and not meeting all the cooling load generated by the roof and glass.
The factory service manuals have a section on Air Conditioning and each one has a matrix giving the expected resultant temperature of air out the vents given specific out side temperatures and humidity.
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-