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1969 CADILLAC A/C REGAS

Started by 1969cadillac, May 24, 2011, 04:51:04 AM

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1969cadillac


Hello out there -  i have a 1969 caddy deville

i have just changed the A/C compressor and receiver dryer

i have replaced all the o rings that i can find

i have 2 questions:

does the AC system really need to be flushed ?as the old compresser didnt fail - just a leaking seal

can i get away with just evacuating the system and adding gas?

the system has also been converted to R134a gas - how much gas go i need ??

orig system is 4lb of R12

thanks , Murray Mules

R Schroeder

#1
You can Google a lot of info, but here iare two to start with.
Roy

http://www.buickperformance.com/ac.htm

http://www.epa.gov/spdpublc/title6/609/technicians/retrguid.html

"Cadillac Kid" Greg Surfas 15364

Murry,
A couple of questions before I can give you  valid answer.
1.Was the oil changed when R-12 was replaced with R-134a, and with what oil (POE, or PAG)?
2. Was the system changed at all from the original configuration, meaning changed to non Back pressure regulator with cycling compressor?
3. Did the system work adequately until this compressor failure?
4. Why did the compressor fail?
Let us know and we can give your an informed response.
Greg
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-

1969cadillac

hello - i will try to answer your questions as best i can !
the system had already been changed to R134a before i bought the car
i rebuilt the engine ,so the system was degassed and opened
i put a bebulit compreessor A6 original  on , new o rings on components remoeved - ac hoses
1. i dont know what oil is now in the compressor -but it has oil in it
2. the system i believe is largely original apart from the compressor - car has only coveresd 4k miles - no joke!
3.system was cold - but NOT real cold!
4.compressor didnt fail - no metal particles - i only replaced the compressor becausde front seal appeared to be leaking oil !

i really just need to know if the system needs flushing - probably not - no shrapnel in system

and how much gas to put in it?

just need the system to work - dont really need to upgrade it!

thankyou need a response ASAP - murray mules





"Cadillac Kid" Greg Surfas 15364

Murrau,
I thought I posted a response earllier, but it seems to have disappeared.  One of the most critical tasks in changing from refrigerant 12 to R-134a is a thorough flushing of all mineral oil from the system.  If more than 3% of the original mineral oil remains, the R-134a combines with it and coats the interior of all components with a "gunk" that inhibits heat transfer, reduces lubrication, and hinders operation of all components.  If your system was left open for any length of time or the oil used when the refrigerant was changed is "PAG", then I woiuld be concerned that the oil has adsorbed substantial moisture from the air and yes, the system should be flushed to ensure longevity.
That said, your comment on cold but not real cold is what is normal when you take the 22% "hit" in performance when going to R-134a with an R-12 system.  I did an article on this "conversion" a few years back in the self starter, looking into the reasons for the loss of performance. It can be overcome with "cubic" money, but I convinced myself that it isn't practical for a car that will be exposed to extremes of humidity and/or temperature with an expectation of good performance,.
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-

1969cadillac

hello - thanks for your thoughts

any idea how much gas to add to the system??

"Cadillac Kid" Greg Surfas 15364

Murray,
If you are using R-12, you charge (vapor only into the port on the POA and slowly, keeping the pressure at below 45 #) until the site glass is clear.  The exact charge would be between 3-1/2 to 4 pounds. Check your service manual for the exact amount of your cars's requirements.
For R-134a, although the "rule of thumb" is 80% of the amount you use with R-12, the correct method of charging this "mongrel" type system would be by starting with about 2-1/2 pounds and then "topping" off the charge using a combination of gauges, superheat measurement, evaporator outlet, and condenser air temperatures.
I know I might seem to be making this a big deal, but that would be the correct way to charge an R-12 system with another(replacement) refrigerant.
Murray, R-12 is available, and again I would recommend using it.  After all, how much do you have invested in your car, and really, how much does it cost to fill it up at the gas station.  Everything is relative.
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-

1969cadillac

Greg - thanks for your reply - i am in Australia - and getting R12 here is like pushing shit uphill!

i really appreciate your info - will gas the A/C on Sunday - so will let you know how it goes!

how did you get 513 cubic inches out of an engine as a matter of interest?

mine is now a 478 - 30 overbore!

murray mules


"Cadillac Kid" Greg Surfas 15364

G'Day Murray,
I did not realize you were "down under". Naturally you have to use R-134a, since R-12 is actually outlawed.  I would suggest starting with about 2-3/4 pounds of R-134a. Charge it through the low pressure connection on the POA and charge it in the vapor phase. This of course after the system has been checked for leaks, and I will have to make the assumption that the oil is correct and the dryer has been changed for the proper type (with R-134a).  With the system settled down after the initial charging, it may be topped off by the method I previously described.
I exadurated Murray.  My engine is a 50/1000 over 500, making it 511 inches.
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-

David King (kz78hy)

134A is on it's way out as well.  So you are trading one obsolete gas for another.  Just FYI.

David
David King
CLC 22014  (life)
1958 Eldorado Brougham 615
1959 Eldorado Brougham 56- sold
1960 Eldorado Brougham 83- sold
1998 Deville d'Elegance
1955 Eldorado #277
1964 Studebaker Commander
2012 Volt
CLCMRC benefactor 197

Director and Founder, Eldorado Brougham Chapter
Past President, Motor City Region

Rare Parts brand suspension parts Retailer via Keep'em Running Automotive

"Cadillac Kid" Greg Surfas 15364

avid,
At this time Murray doesn't have a choice. manufacturer of R-134a (the refrigerant itself) is slated for a 2030 phase out , and the replacement HFO 1234yf is not yet available for consumers.  When it is it will wholesale for $50+ per pound.
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-