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  #16  
Old 04-16-2011, 01:26 PM
vstech's Avatar
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all NAPA stores stock R12 in cans. you need the cert 408 I believe, but it is easy to get online... open book test. for like 15.00
the cans are pricey, at like 25.00 each retail, if you run a shop you should not be getting cans, you should be getting drums... around $500 new.
and getting a sealed cylinder of 12 from craigslist is even cheaper... I've gotten them for free, to $100 or so for 30 POUNDS of 12...
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Last edited by vstech; 06-06-2011 at 06:13 PM.
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  #17  
Old 04-16-2011, 01:29 PM
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Quote:
Originally Posted by leathermang View Post
"I'm assuming this is still the original question." --YAK

Not really... this thread has been designated a sticky to become a standard reference guide...
So your input on anything you think should be addressed is welcome.... you do not have to limit your replies to the original OP question....
And you are doing a great job !!!
yeah everybody post all the questions and info on here you want. I'm going to try and organize the answers, and weed out the problem info. I'll also answer questions, anybody else answering questions please quote the post you are answering.

this is looking like a great start to the reference, and I'll devote a lot of time to it. (it's my field)
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #18  
Old 04-16-2011, 03:31 PM
sjh sjh is offline
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The units and standards used for pressure measurements are very confusing.

Normally atmospheric pressure is called 1 atm. Now the fun begins:

1 atm ~ 1 bar (there's a 1% error)
1 atm = 14.7 PSI (pounds per square in)
1 atm = 760 mm Hg (millimeters of mercury)
1 atm = 29.9" Hg (inches of mercury)

and just for fun

1 atm = 101,300 Pa (Pascal) = 101.3 KPa [Metric]

One other common identity is -

1 mm Hg = 1 Torr
1 mm Hg = 1,000 microns

Another source of confusion is what does one choose to call zero pressure. Normal atmospheric pressure may be defined as zero or a perfect vacuum may be defined as zero. The difference protocols are designated either "gauge (G)" or "absolute (A)". So -

At norrmal atmospheric pressure: 14.7 PSIA = 0.0 PSIG

At a perfect vacuum: 0.0 PSIA = -14.7 PSIG

I believe there is one other potential source of confusion but those experienced with AC systems will have to verify this statement. Starting at atmosphere and then drawing a partial vacuum the system would start at 1.0 atm and then progress to 0.8 atm, then 0.6 atm, etc.

In AC systems it appears they use gauge (G) readings and inches of Hg. So starting at atmosphere and drawing a partial vacuum the system would start at a reading of 0.0" Hg and then proceed to -5.0" Hg, then -10.0" Hg etc.

So at a vacuum the pressure would read -29.9" Hg and while it is not normally written the - 29.9" Hg is understood to be a gauge (G) reading and not an absolute (A) reading. And, from what I see in the AC literature, the minus sign is normally dropped and they usually don't say mercury.

So, at the end of the day, a perfect vacuum maybe indicated by any of the three statements -

Perfect vacuum = 0.0" Hg (absolute scale)
Perfect vacuum = -29.9" Hg (gauge scale)
Perfect vacuum = 29.9" (gauge scale, no minus sign, no mercury)

Last edited by sjh; 04-23-2011 at 09:04 PM. Reason: Make consistent with DIY thread
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  #19  
Old 04-16-2011, 03:52 PM
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Quote:
Originally Posted by vstech View Post
Great question.
several levels of answers can be dependent on what the 134 "conversion" entailed.
first, the Oil in the system. if you do not know what kind was used, it's best to replace the compressor, the expansion valve, and the compressor manifold, with the dryer and flush the remaining coils with oil/refrigerant flush, then add the correct amount of mineral oil to the system, pulling a hard vacuum, then weighing in the correct volume of R12.
this is the BEST method to convert back to 12.
PAG oil is not compatible with R12, Ester is. if you don't know, it's best to assume PAG was used, and do it right. however, since doing it wrong will destroy your compressor, requiring you do do all that stuff, if the wrong oil is used, and will not if Ester is in there, simply evacuating the refrigerant, measuring how much oil came out with it, and replacing that with the same amount of ester oil, then flowing the weighed amount of R12 will put the system back to R12. however you will still have the 134 fittings on the system... if you try to remove them, you can damage the lines (don't ask how I know this) this is why it's needed to replace the compressor manifold.
then lastly the 134 sticker needs to be removed.
Thank you for your detailed response. I appreciate it.

When I last evacuated and charged the system I used ester oil. I don't know what the car originally came with. I do plan on changing the compressor. However, if I could run the system on R12 for a while before changing the compressor and any lines, that would suit me nicely.

Are you saying that I cannot swap the R134 fittings for R12 fittings without damaging the lines? Or, are you saying I must be careful or I will damage them?
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  #20  
Old 04-16-2011, 08:09 PM
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the fittings on some conversions can be removed, but it's impossible to know which ones can and which ones can't... better safe than destroyed...
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #21  
Old 04-17-2011, 12:20 AM
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Regarding the nitrogen test...

is one to have the system oiled or not? Seems to me not as when you evacuate it you would lose some oil.

If no oil, do you simply evacuate the nitrogen then open one fitting to add the oil... then close it back up and vacuum down?

Perhaps it has been covered and I am just missing something. It is late and I am sleepy again
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  #22  
Old 04-17-2011, 12:53 AM
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evacuation should not remove much oil at all... RECLAIMING will remove a significant amount of oil, but the reclaiming machine should separate and store the oil removed separately.
an existing system after evacuation, to test for leaks, with dry gas, and trace R22 oil should not be an issue.
fresh flushed system, may need oil for maximum leak free, but there's no good way to distribute the oil without a full charge of refrigerant... so it's not important for spotting leaks.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #23  
Old 04-17-2011, 09:09 AM
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Quote:
Originally Posted by leathermang View Post
The MB AC FSM suggests as you put the system together... spacing out the total oil you are going to use in several places.... so that the entire burden of getting it spread around is not borne by the refrigerant..
This is ESPECIALLY IMPORTANT ON SYSTEMS USING THE R4 Delco since it is totally dependent on refrigerant carried lubricant.... lacking an oil sump itself..unlike most other AC compressor models ... even earlier models like the York..
yup. this will certainly aid the distribution of the oil into the system, but!!! it will not flow in nitrogen, so it will not coat all the seals and surfaces of the lines etc without the refrigerant charge.
my point here is on the OP's statement of his system not holding vacuum until the oil got into the system,,, it's not important for a pressure test. it is CERTAINLY important to have the exact volume of oil, distributed during installation of the components in the quantities specified in the FSM.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #24  
Old 04-17-2011, 11:27 AM
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I do not think the oil for the compressor is or should have to be counted on to seal the system.... as NYLOG of the proper color would be used on the o-rings and gaskets as the system is put together..
So the nitrogen would be used with the oil already in and spread out ..... do nothing except provide pressure and a SNIFFABLE refrigerant ( R22) to use as leak detection...
The compressor is not going to be used until the system is certified leak free...and the proper refrigerant is installed... so that can be used to carry the lube around and keep the compressor lubricated.
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  #25  
Old 04-17-2011, 01:15 PM
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So far this is what I have gathered as the correct "process" of refilling the system after rebuilding it. This is assuming you have replaced all the o-rings, parts, etc.

1. Add oil to the system in various spots so that it is easier on the system to circulate.

2. Add PRESSURE to the system to check for leaks, etc. with 4oz R22 in, CO2, or Dry Nitrogen.

3. Once pressure has been added and no leaks detected, vacuum down the system to remove moisture.

4. Add freon of the proper amount to the system and "pulse" the compressor to get it circulating.

Is this correct?

Also I'd love to see opinions on different compressors and what makes certain R4's different from others and what the CORRECT R4 compressor for our car is.

Last edited by vstech; 04-18-2011 at 12:41 AM.
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  #26  
Old 04-17-2011, 01:36 PM
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I have not seen any instructions concerning " pulsing' the compressor...
I think once you are ready.. you install all the refrigerant which will do naturally..with warm water at the base if using a small can.... figuring that you will get enough in to activate the low pressure cut off switch... otherwise it would need to be jumped to use the compressor to help load the system.... .. with the windows down, system on HIGH COLD... and put the refrigerant in... in the form of VAPOR... not LIQUID ( unless you really know what you are doing .. otherwise you can crack the reed valves in that new compressor... or an old good one for that matter )...forceD air blowing into the condensor... etc... like Vstech mentioned above...
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  #27  
Old 04-17-2011, 02:16 PM
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on a 95 S320, I"m curious what other refrigerants could be used. The r134 doesn't really cut it. I had converted R12a a while back, and it held for 3 years under extreem temp variations...
I"m thinking about taking the system apart and checking it. Could argon be used instead of co2 or N??
I"m in Canada and R12 is a huge no no... What other refrigerants would be good to use?? Even when the R134 was working 'properly' according to the tech, it still didn't cool the car worth a damn...
BTW, window tinting is illegal here unless it's factory tinted glass. Car is a gold color with mushroom interior....
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  #28  
Old 04-17-2011, 02:40 PM
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Yes, Argon is fine to use.
I do not recommend any except R12 or R134a for several reasons...
I suggest that you first be sure your system is in good shape.. have you cleaned your evaporator fins ? This is something seldom done and sometimes not fun or easy... but very very important... if they are clogged up with whatever.. you are not getting good air flow over those cold fins.... so your air can not be cold in the car...
Then... your condensor... the bottle neck of all AC systems... think about upgrading the fan and being sure your fins on it and the radiator behind it all straight and clean..
Those would be the most important and effective things to start with... and assume they will allow the R134a to do what you need for cooling...
I have three autos with R134a here in the middle of Texas... and in a humid spot to boot.... and they all do just fine...
Be sure your basics are up to par before considering going to some off the wall refrigerant.....
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  #29  
Old 04-17-2011, 05:39 PM
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Quote:
Originally Posted by amosfella View Post
on a 95 S320, I"m curious what other refrigerants could be used. The r134 doesn't really cut it. I had converted R12a a while back, and it held for 3 years under extreem temp variations...
I"m thinking about taking the system apart and checking it. Could argon be used instead of co2 or N??
I"m in Canada and R12 is a huge no no... What other refrigerants would be good to use?? Even when the R134 was working 'properly' according to the tech, it still didn't cool the car worth a damn...
BTW, window tinting is illegal here unless it's factory tinted glass. Car is a gold color with mushroom interior....


Quote:
Originally Posted by Matt L View Post
If a factory system is not cutting it in Canada, don't blame the refrigerant. Something else is wrong.
AMEN!

in 95, the ONLY refrigerant available is R134a.
SOON the refrigeration field will be changing all systems to... get this... LIQUID CO2!!!
go figure.
anyway, until that happens, you need to have your system working properly and all components inspected.
as mentioned both coils need straight fins, and need to be free of debris.
are you sure, the CORRECT amount of PAG oil is in the system? too much oil, will drastically affect cooling.
have you had a visual inspection of the evaporator coil? any leaves/compost/dog hair in there? get it out!
has the system ever had a compressor fail? is the current compressor working properly? By 1995, manufacturers were well versed in the failings of R134 refrigerant, and the cars were well designed to function properly.
I think you would be best served with pulling the TXV/flow piston... not sure what your vehicle uses. pull the dryer, pull the rubber hoses, and flush the coils with oil/refrigerant flush. then replace all seals, and hoses, and the TXV, then either replace the compressor, or use it based on the debris that comes out. ANY junk comes out with the flush, and the compressor is toast.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #30  
Old 04-17-2011, 08:51 PM
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I cleaned out the core last august when I had the radiator out to replace it... I worked the thing over really good with an air compressor. Blew out a lot of road salt, sand, bugs, etc... There are 2 places where about half a dozen fins max are folded...
Not sure about the oil... How would one evacuate the oil out of the system to put in the right amount?? Can that be done without taking the system apart?? Or opening it up??
I"m unsure about a compressor fail... I'm the 4th owner of the car... I don't have a receipt for one, I'll put it that way. The previous owners seemed to take good care of the car, and keep good receipts...
Would the TXV/flow piston be the same as an expansion valve??
Even r134a is hard to get here in Canada. The Canadian government is recommending that people use duracool or r12a. Something about Canada's environmental initiative...
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Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic
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