R12 to 134A, How much? refrigerant

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  #1  
Old 11-05-02, 06:29 PM
Richard J
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Question R12 to 134A, How much? refrigerant

Do to compressor lock up I have converted to 134A. New accumulator, "o" rings and main compressor hose. Radiator and condenser removed and cleaned. condenser and evaperator flushed with Superflush. 28-29in of vacuum held for 24hours so I was satisfied with that. I mistakenly read that the R12 capacity is 2 1/4 lb. I added 80% or 28oz. For this I used a hanging basket scale with 3 cans in basket and hose taped to side and gauges hanging nearby. Air temp 70 deg, low side 20 lb, high 220 lb, 1500rpm, coolant temp 212, aux fan on and small box fan in front of car (very little help, inside open garage). At idle, low side 24 lb, high 180 and coolant temp 198. Decided to stop there and see how well it worked at that point. Disconnected the hoses and the low side 134 adapter is leaking. This is the new schrader in the new accumulator. Had to find a wrench to take off the 134 adapter, then had to find the valve tool. It stopped leaking, but how much did it loose? I added 2oz. Pressures seemed the same and drove it. 70 deg day and stopped in traffic, temp goes to 205 and stays there with aux fan running. I start rolling and temp is 179 deg almost immediately and stays there up to 80mph. It sounds like clutch is cycling, but it's the main fan going off/on. I put the gauges on and the high side is all over the place. At 240 lb the fan comes on. Coolant temp drops, high pressure drops to 160. Fan stops, coolant temp goes up, pressure goes up to 240 and the cycle repeats. Clutch is on during all of this. As I now know that total R12 capacity is 2 3/4 lb or 44 oz, I should have put in 35.2 oz of 134.
?? Was 2 oz enough and will another 7 oz stop the cycling. The book says the fan control switch opens above 233 psi and closes below 185 psi.
Should I worry about the 233 top or should I worry about the 185 so that the fan doesn't turn off? The weather is too cool right now to know how high the high side may go on a hot day.
I have found a dozen R12 temp-press charts. Does anyone know the address for a 134A chart on the internet? The best chart I have found for R12 had high and low press, ambient and outlet temps and humidity, all on one chart.
Sorry this post is so long, but I don't expect the answer to be that simple either.
The air system is the C68 electronic in a '87 4+3 Corvette coupe. ( temp is set and the computer adj everything, including fan level)
 
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  #2  
Old 11-06-02, 10:09 AM
Joe_F
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Why did you convert to R134A? It may have been better to stick with the R12 system in this. Cools more efficiently .
 
  #3  
Old 11-06-02, 01:03 PM
Richard J
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Because I can't buy R12.
Because I want to charge the system myself.
Because, if it should develop a leak I wouldn't be spewing R12 into the atmosphere.
Because everyone and his uncle says it's less efficiently, but no one says by how much
This system is providing cold air right now (allowing that the weather is a cool 75 ). The problem is that the electric radiator fan is being turned off by the ECM.
 
  #4  
Old 11-06-02, 04:52 PM
Joe_F
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1) Tests have been shown that R134A is not as efficient as R134A
2) Each vehicle varies in what it takes to convert.
3) Some vehicles will not perfom well with R134A
4) Newsflash: R134A isn't good for the atmosphere anyhow.
5) Do you have the service manual or diagram to the system?
 
  #5  
Old 11-10-02, 11:42 AM
Dan Meyer
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Richard J
I haven't been at this board for awhile. Do you still need help?
I don't want to post info that's not needed. I will probably check back Nov 11 or Nov 12
 
  #6  
Old 11-10-02, 01:17 PM
Richard J
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Yes , I do still need help. I have made one and only one change since the original post. I had also posted this same question on a Corvette forum. A guy on there that had made the same conversion, insisted that in cool weather the clutch should be cycling more frequently and that the low-side pressure should be 35psi to prevent freeze up. The low-side pressure switch is ajustable. I made this change and the clutch is cycling. The "fan control switch" mentioned earlier is controled by the ECM and has a 15 second delay. In between clutch cycling the high side never gets above 150-160psi. As I said earlier the fan control switch turns the fan off under 185psi. Within the 15 seconds the clutch cycles twice, the fan goes off, coolant temp goes up, high side press then goes up to 240psi, the fan comes back on and the cycle repeats. It turns out that the original 2 1/4 lb of R12 is correct. I'm told the service manual is incorrect. Thanks
 
  #7  
Old 11-11-02, 05:01 PM
Dan Meyer
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From what I read it appears you did the proper procedure in preparing your system for retrofit. You're leaving out important info: are you getting cold air out the vents and what is the temp?
Anyway, it may be that you have air in the system. Did you purge the hoses before you charged the sys? With the engine in fast idle (1000 - 1200 rpm) , a/c full cold, blower on high, feel the line coming out of the evaporator. If it gets cold, warm, cold, warm etc. then you have air in the sys. Let the sys. stabilize overnight. Then DON'T start the engine and take press. reading on the low and high sides. the press. should be about the same as the ambient air temp. If it is much higher, you have air in the sys.
Here's some t/p numbers for R-134a: the first no. is the ambient air temp, the second no. is what the gauge press. should be: 50-45.5, 60-57.5, 70-71.2, 80-86.8, 90-104.4.
Your low press. switch is set way too high. It should be set to cycle @ 19 to 21 psi. High press. should be no higher than 2.3 to 2.5 times ambient air temp. at fast idle.
When charging it takes approx. 80% R-134 of the amount for R-12. Put in approx 60% then SLOWLY add R-134 watching high press. and vent temp. When high press. reaches 2.3 to 2.5 times ambient air temp OR vent temp. starts to rise - then STOP!! It's the best you're going to get.
Unless you live in the tropics or you have a heated garage, you may have to put off your work until summer.
 
  #8  
Old 11-12-02, 10:48 PM
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Richard,
I've converted all of my old vehicles to R134 for the same reasons.
What Dan is telling you is correct. The only vehicle I had any problems with was an old chevy. It didn't cool very well at idle. My fix (which worked great) was to install an electric fan in front of the condensor.
Have Fun!
 
  #9  
Old 11-13-02, 04:03 AM
wolfsmane
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richard, go to this link and try this site. they specialize in automotive a/c, retrofitting, and have a wealth of information available. let us know what you find.----> http://www.ackits.com/forum/index.cfm
 
  #10  
Old 11-13-02, 07:08 AM
Dan Meyer
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Dirty Dan
You could have solved the low cooling at idle by installing an orifice tube which was one size smaller (ford blue)
 
  #11  
Old 11-13-02, 09:11 AM
Richard J
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Sorry that I haven't responded. I will get back to this as soon as I can. My elderly uncle is in the hospital. I have been trying to help my aunt and educate myself about medicare, medical and skilled nursing homes.
Vent air, I think is what it is supposed to be. Vent temp is usually about 10 degrees below the setting. If I set the digital temp display to "65" , the vent temp is 55 degrees. As I said before, What I'm fighting is that the "too-low" high-side press is turning off the radiator fan at idle.
Thanks, I'll be back on it as soon as I can.
 
  #12  
Old 11-13-02, 03:57 PM
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Waht do you mean by Ford Blue???? This was a Chevy ccot system.
Please explain that to me.
 
  #13  
Old 11-13-02, 08:16 PM
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A point that seems to be missing is the danger of handling refrigerant gases or liquids.People whom are unaware of the properties of these chemicals are exposing themselves to consequences that are irreversible.Blindness is a biggie,frostbite another although relatively minor.I agree with Dan Meyer on most aspects, but a/c work can be dangerous for diy's.Have someone remove the refrigerant and have someone replace it also.Do all the other repairs you want no danger unless 2 minutes into the job the accumulator decides to release more refrigerant.SAFETY GLASSES AT ALL TIMES PEOPLE.beginning to end,maybe you'll be lucky.Refrigerent displaces oxegen so do your work in a well ventilated area.Don't smoke near an r-12 system while working on it either.Burnt r-12 produces phosgene gas(nerve gas)just a little tip.
 
  #14  
Old 11-14-02, 11:02 AM
Dan Meyer
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Dirty Dan
The orifice tube on a GM car is white which indicates the size. Ford uses a smaller size and it is blue. But they are interchangeable.
 
  #15  
Old 11-14-02, 01:26 PM
Joe_F
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Dan Meyer: Who says they are interchangeable? Does the OEM recommend it?

Each vehicle varies with the conversion that is needed. There is no set formula for converting an R12 vehicle. If serviced properly, the vehicle should stay R12...R134A will give disappointing cooling results in many R12 equipped applications.

Always stick with the OEM procedures. I agree with Davo. A/C work is NOT something for the DIY person without the right tools, procedures, and know how. Your life, health and safety are not worth it.
 
  #16  
Old 11-14-02, 01:52 PM
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Thanks for the info Dan. I've got a friend who's wanting to swap over a '91. We'll give that a try.
 
  #17  
Old 11-17-02, 10:43 AM
Dan Meyer
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Joe F
You're contradicting yourself. First you say "does the OEM recommend it?" and then you say "there is no set formula for converting an R-12 vehicle".
Well, you're right, there is no set formula. That's why there are little "tricks" that can be used to get the job done. I'm sure many of the professional mechanics on this board have many, many tricks that they use that are not OEM recommended. Probably some that the OEM's don't even know about. And that's what this board is all about.
I'm a Petroleum Engineer by trade. But one of my hobbies is air conditioning work. And I do know some tricks about it.

Dirty Dan.
Dropping down one size on the orifice tube will give better cooling at idle and city driving with a retro fit. On the open road at high way speeds it may give lesser cooling. It's a trade off when converting from R-12 to R-134a. There is such a thing as a VOV which is supposed to be a variable orifice valve (changes opening based on pressures). I've heard mixed reviews about it. I've never used it on any of the retro fits I've done as I've just dropped down one size with good results (even on high way driving).
 
  #18  
Old 11-17-02, 06:30 PM
Joe_F
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Dan:

No contradiction by any means, I believe you misread my post. Does a Corvette require different retrofitting than a 1979 Trans Am? Sure does. Condenser designs differ. Compressor designs differ. Systems differ. My 79 T/A has an A6 compressor. You can throw that thing down a mountain and it will still blow ice cubes.

Since each vehicle differs:

That is why you cannot say what needs to be changed on each
vehicle. Each will differ in what it requires. Some systems simply will not take well to R134A conversion. I put Autofrost in my 84 Delta 88 in 1997. It will freeze the hair on your chest to this day. I changed the O rings, added oil and charged it up. That was July 1997. Do it on a Ford product, such as an FX15 compressor and it will puke it out. Fords tend to eat up alternative refrigerants like AF.

As to "does the OEM recommend it", you DEFINITELY misread my post. Put the wrong orifice size in a conversion and you might be eating a compressor warranty return. You must follow the rebuilding companies instructions to the letter to validate the warranty or it will be a headache later on. Many companies are very strict about failure claims. If the job isn't done right, they will pass you a gooseegg with regard to credit and chalk it up to a bad installer's job.

Deviating from what the OEM states should be done is bad business. We're not talking swapping synthetic for dino oil or blending your own oil. AC work is serious business as Davo stated earlier. It is no longer DIY work without the proper tools and know how......

----
I'm sure many of the professional mechanics on this board have many, many tricks that they use that are not OEM recommended. Probably some that the OEM's don't even know about. And that's what this board is all about.
----

I take exception to that and so do most of the pros here. A trick that is not OEM recommended is not a trick to do. It may not be safe, prudent or cost effective. For example: If the OEM says use a DVOM to check something, there's good reason to follow what they say to avoid injury and property damage. Sure an adjustable wrench can fix a BMW, but would you want to do that? Always stick to the OEM as a guideline. Without fail. Changing orifice sizes may have an effect on the system in ways you don't know about.

Davo said it best and I agee with him 100%.
 
  #19  
Old 11-18-02, 01:52 AM
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Dan M,
We're still going to give it a try. The gauge set will tell us right away if the Ford tube is causing trouble. I agree with you that there are many tricks commonly used that the OEM doesn't recommend. There are more items on which the OEM is silent. That doesn't always mean you shouldn't do it.
I never saw Pontiac recommend putting 72cc heads and/or a Turbo 400 long shaft on a '72 Ventura, but believe me, it worked great. With the Predator Carb,which wasn't recommended, it turned 11.2 quarter. My Chevrolet shop manual doesn't recommend using Trans-X in my 700R4, it worked fine and cleared up my shifting problems.
The OEM's information is great, but it is not nearly all inclusive. I tend to think that the OEM information is leaning towards the best interests of the OEM, not the vehicle owner.

Just my $0.02
 
  #20  
Old 11-18-02, 05:42 AM
Joe_F
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All of those things you mention may effect emission control, require adaptation in many regards and may not work well in all platforms. You also have to understand how the OEM setup works before deciding that swapping something would work better. If you don't understand the relationship between compression and horsepower, lift and duration in a cam, or head porting and polishing, exhaust and the rest of it, you're shooting in the dark trying different things. Sometimes it works, other times, you lose, sometimes it's fatal or a waste of time.

None of those is generally life threatening. Servicing AC improperly can lead to property damage and injury as Davo mentioned.

Trans X is a band aid for a real problem, so that's why the OEM won't recommend it.

A 72 Ventura would have benefitted more from overdrive than a Turbo 400, but again, it requires adaptation depending on the powertrain being used.

A Predator carb also isn't emission legal, so that's why it's not "recommended". An Edelbrock or a Q-jet would be and would work just as well and deliver reasonable fuel economy over a Predator.

Be careful what you recommend. You do not know the skill set of the person attempting the repairs, what tools and techniques they have, the information they have and how they will do the actual repair. I'd hate to see someone get hurt because they ASSumed something!
 
  #21  
Old 11-18-02, 06:09 AM
Dan Meyer
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Dirty Dan, thanks for your support.
If everything is done according to OEM standards, what's the sense in having this board. Just take the car to the dealer for work
As I said, I believe that this board is for DIY'ERS like me to learn tricks of the trade from the kindness of the pro's who've "been there and done that" and who out of good will help those of us who need help.
In return, I try to offer what knowledge I have in the area's I have expertise in.
Doing everything "by the OEM book" may be the safe and prudent way, but it doesn't lead to new ideas and methods. If everything in life was done "by the book" we would all still be riding horses.
Since I'm on "my soapbox" I want to thank all of you pro's for your time and effort in helping us DIY'ers.
 
  #22  
Old 11-18-02, 10:02 AM
Joe_F
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Dan,

Sorry to disagree, but it's not correct .

Why publish the OEM book? Why is it done? To service the vehicle CORRECTLY . Most folks say, "Ah the hell with the book!". Why? Simple: Lack of knowledge. The OEM builds the car and they know the most about it. More than me, more than you, more than mostly any of us out here. We can and should start with what they prescribe as far as maintenance. Once we master (not understand, but master) how things work on that perspective, then we can perhaps "experiment".

To do so without understanding what the OEM says or how things work is a gamble. It could be expensive, time wasting, or even dangerous gamble, depends on how you look at it and what you value, your safety and your property or trying to save a buck. My life's worth more than any $$$ I might save taking a shortcut.

-----
If everything is done according to OEM standards, what's the sense in having this board
----
I completely disagree...

If everything were done to OEM standards, half the questions on this board would be answered in half the time and fixed right the first time . Trust me, with 10,000+ posts under my belt here, Knuckles and I have answered it all. Lol. I repeat myself probably 15 times a day when the answer is right there for most folks to see. Shoot, reading the top of the forum's page answers half of the questions for most folks!

Think about what you are saying. If you go to your doctor and you have a symptom, would you want him to guess on you? Or, would you want him to try some drug on you he concocted in his basement that didn't have FDA approval? How about if he whipped out a 1982 version of the medical book and laughed when you asked if that was the most current thing he had to treat you?

You'd call him a quack and run for the hills. Shoot, I would! You'd want him to understand your symptoms, consult with history/written authority on it, use known and tried practices and medicines that work, but you surely wouldn't want him to experiment on you!

Now think of your car in the same light. Auto repair is much the same way a doctor fixes you, some of the same logic is used in repairing automobiles.

Automotive repair is as professional and similar to medical diagnosis as anything out there. Those that don't prescribe to this theory are FAR from professional in my book .

My .02
 
  #23  
Old 11-24-02, 08:53 AM
Richard J
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Wow! I haven't had time to work on the car or check back in here for the last two weeks. I didn't know that it had turned into a pissing contest. I'll be able to look at it after Thanksgiving. I can say that even though 134A may be less efficient, I have had complaints from my passenger that she was too cold. This past week we were in the high 80's several days. I did use the white orifice. As I have said repeatedly, the problem isn't an ability of the system to cool. The problem is that it is turning off the radiator fan at idle.
 
  #24  
Old 11-24-02, 09:35 AM
Joe_F
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No pissing contest here.

There are diferences of opinion, which is fine.

Differences of FACT are another matter.
 
  #25  
Old 11-24-02, 03:56 PM
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"A 72 Ventura would have benefitted more from overdrive than a Turbo 400, but again, it requires adaptation depending on the powertrain being used."

Joe F,
You must be a youngster, there were not a whole bunch of GM Auto overdrives in the early '70's. I liked the Auto Tranny with the Slapstick. (I never missed a shift)

"A Predator carb also isn't emission legal, so that's why it's not "recommended". An Edelbrock or a Q-jet would be and would work just as well and deliver reasonable fuel economy over a Predator."

Once again, emission legal wasn't a problem in the '70's. As far as I know, Edelbrock or Holley still doesn't mfg a variable CFM carb. I'll grant you that I sure would have gotten better gas mileage, but acceleration was my primary interest. Driven correctly, the Predator gave you the low end torque of a two barrel and the high end fuel flow of a 4bbl.
 
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