Author Topic: r134a conversion  (Read 3595 times)

Offline Hankk17

  • Posts: 255
  • Name: Hank Kuczynski
r134a conversion
« on: March 25, 2012, 10:30:38 AM »
I've read some of the other threads here on this subject and don't want to start another "thread of tangents"  lol

I know r134a produces lackluster cooling so lets get that out of the way first.  I'm reading up on how to do the conversion and something in the manual confuses me about the amount of refrigerant I should be using.  it says "3 3/4" pounds and internet calculators convert that to be 60 ounces:

Answer: 3 3⁄4 (3.75) lb = 60.0000 oz  from http://www.metric-conversions.org/weight/pounds-to-ounces.htm

is this a proper conversion?  does "pounds" here actually mean weight or are they talking pounds of pressure in the manual?  any idea how many 11 oz cans of r134a equal 3 3/4 pounds?

-Hank
Wherever you go... There you are

Offline Don Boshara #594

  • Posts: 232
  • '40 6019S
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Re: r134a conversion
« Reply #1 on: March 25, 2012, 01:00:35 PM »
It's weight. You would need 5-1/2 cans.
1940 Sixty Special
1966 Mustang Cpe

Offline pauldridge

  • Posts: 265
  • Phil Auldridge
  • Name: Phil Auldridge
Re: r134a conversion
« Reply #2 on: March 25, 2012, 08:18:15 PM »
That is a LOT of refrigerant!  I've installed lots of A/C systems, doubt if I've ever used more than 3 cans on an empty system, and that with a rear-trunk-mounted evaporator system and miles of hose.

although not a perfect approach, I've had 100% success with just adding refrigerant until I get around 180-200PSI on the high side of the compressor.  I DO hope you are using a gauge set to add the refrigerant (about $50 on sale at Harbor Freight, and a great piece of equipment to have on hand).

To make a successful conversion:

1) attach a vacuum pump to the system (engine off) and run it about an hour or so to remove any system-killing moisture

2) To test the integrity of the system, close of the pump line, but leave your gauges attached overnight.  If you still have the same vacuum reading next morning, you're reasonably assured of no leaks... otherwise, you'll need to add an UV dye to the refrigerant to determine where the leak is.

3) Start the car up, block your accelerator pedal to get about 1500 RPM's or so, turn on the A/C, and start interjecting the refrigerant into the LOW PRESSURE side of the compressor (NEVER open the valve on the gauge to the high pressure side when the engine is running)  Be sure to add some R-134-compatible  PAG oil to lubricate the compressor.  This is most easily done by just buying a can of R-134 with oil included, available at most parts stores.  A single can w/lubricant should be sufficient. 

4) Every 30-45 seconds or so while adding refrigerant, you can momentarily turn the can upside down then right side up again to expedite the transfer.  Be patient, it can easily take 5 minutes or more to empty a single can of refrigerant

5) continue this procedure until the high pressure side reads 180-200 PSI as stated earlier (different systems may require different pressures, but you'll be in the operational ball park at these readings).  And, NO, a just a bit more refrigerant/pressure for the wife and kiddees is not necessarily a good thing.  As soon as you're getting some decent cold air out of the system, with pressures somewhere in the stated range, you should be good to go.

A few other notes:
*Adding refrigerant is most effectively done with ambient temperatures in the 80 degree or higher range

* Best to set up an external floor fan blowing on the radiator while charging the system.

*Before turning on the valve into your A/C system, be sure to purge your gauge lines of air (and moisture).. just crack the connector on the hose right at the compressor connections and open the valve to your refrigerant can until you see/feel a bit of refrigerant coming out.  For this reason, the best gauge sets are those which have shut off valves right at the compressor connection to allow you to purge.


After all that, I should say that some 10 years ago I bought one of those quicky R12/R-134 conversion kits at the auto store.  You know, a couple of adapter fittings, 2 cans of R-134, and a hose and valve to fill.  My old Chevy truck A/C had long since quit working... I didn't evacuate the system, or anything.  Just slapped those adapter fittings on there, dumped in the new R-134 cans, and I swear that truck is still blowing cold air 10 years later!  Point is, these systems are pretty simple and goof-proof, but as long as you're doing it, no reason not to take a few extra precautions to save you grief down the road!
Phil Auldridge
Austin, TX
1940 60S as well as MGA, Stingray, '39 Ford Coupe, BMW 3.0 CS, '59 Jaguar, '51 Hudson Hornet, '64 and '70 Mercedes roadsters, and Nash-Healey LeMans Coupe

Offline curly

  • Posts: 290
  • Name: T Lewis
Re: r134a conversion
« Reply #3 on: March 25, 2012, 10:55:15 PM »
I keep hearing that 134a doesn't cool as well as R12, I totally disagree.  My experience with many vehicles, both  stock 134 or converted from 12 shows that 134 cools just as well as 12. ( And that is living in the desert of Az ---Yuma!  :o )

When converting to 134, you want to install about 75% the amount of R12.  Barrier hoses are recommended, but I have never used them. (134 molecules are supposedly smaller and will pass through standard 12 hoses.  Never been a problem for me.)

Agree with the above comments on the Vacuum above..... but holding a vacuum doesn't always mean there is no leak. On Friday I evacuated a jeep wranglers A/C system and it held vacuum for 2 hrs.  As soon as I added refrigerant, the low side cycling switch began to leak.  I have experienced the same thing on other vehicles.

Placing the refrigerant can in a pan of warm (not hot) water will help speed up the transfer from the can to the vehicle.  As the can empties, the psi drops, slowing the transfer.  Warming the can will help eliminate that.

Be careful turning the can upside down. Slugging the compressor with liquid refrigerant is not good for the compressor.  Whether it is the A/C compressor or the engine, liquid cannot be compressed.

T Lewis

Offline TJ Hopland

  • Posts: 4069
Re: r134a conversion
« Reply #4 on: March 26, 2012, 06:26:15 AM »
Do you ever do a pressure test using shop air?  Does not seem like I have ever seen fittings to do that.

My 80 Eldo cools fine as long as the car is moving and rpm's are up.   At idle in traffic its not much better than ambient.  I remember these things when they were new being able to freeze you out even at idle.  I didnt do the conversion on the 80 so I have no idea what if anything was updated.   Its performance was pretty much the same experience I had on my 93 Roadmaster.  That one I got a full 'kit' and because of a leak in the condenser I even got the 'updated' one of those too.   I sort of remember the first factory cars with 134 were like that but after the first couple of years they made enough changes so things were more what we were used to.    I have no idea how the 70's-80's systems compare to the older stuff when converted.  The few older cars I have dealt with didnt have AC.   
« Last Edit: March 26, 2012, 06:28:23 AM by TJ Hopland »
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73 Eldo convert w/aftermarket EFI
75 Eldo rusty but trusty
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And other assorted stuff I keep buying for some reason

Offline Roy Schroeder

  • Mr. Mulberry
  • Posts: 1984
Re: r134a conversion
« Reply #5 on: March 26, 2012, 06:49:21 AM »
You guys might want to read through this before doing anything. It is more than just changing the gas in the system.

http://www.e38.org/pparish/gm-rp.htm
ROY SCHROEDER 
WISCONSIN
1978 Cadillac Coupe DeVille
It's only original once.

Offline Dave Shepherd

  • Posts: 1723
Re: r134a conversion
« Reply #6 on: March 26, 2012, 10:31:06 AM »
You guys might want to read through this before doing anything. It is more than just changing the gas in the system.

http://www.e38.org/pparish/gm-rp.htm
  Agreed, done right this is not a simple drop in.

Offline "Cadillac Kid" Greg Surfas 15364

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Re: r134a conversion
« Reply #7 on: March 26, 2012, 08:53:52 PM »
The question I might ask is WHY change from R-12 which is still available in the US at about $50.00 per pound?  In order to satisfy the EU demand for reduction of greenhouse gas emissions, the EU has mandated that all currently produced vehicle AC systems cannot use R-134a.  In order3r to not disqualify themselves from European markets the American vehicle manufactures have followed suit and are currently producing vehicle AC systems using the latest and greatest refrigerant HFO-1234yf.  It is ESTIMATED to cost somewhere around $80.00 per pound, and is said to be (another) "drop in" for R-134a, with only a reduction of cooling capacity somewhere around 5 to 7%.
There are so many "urban Myths" regarding R-134a vs. R-12 that it is difficult to know where to start in a fair and unbiased comparison or an explanation of the true causes of decreased performance so I won't try.  Just be aware that just like the GM Retrofit paper warns "once the vehicle has been ""retrofitted"" it costs a lot to change it back".
I have done a few "unretrofits" for people and it is a time consuming (READ COSTLY) and thankless task.  You have to spend a lot of money to get what you started out with.
R-12 is out there and readily available.  Use it.
Greg Surfas
Cadillac Kid-Greg Surfas
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
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76 Coupe deVille
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Offline curly

  • Posts: 290
  • Name: T Lewis
Re: r134a conversion
« Reply #8 on: March 27, 2012, 07:17:20 AM »
R-12 may be available for $50/lb, but unless you have a MACs license, you cannot buy it.  @14/lb, 134a is available over the counter for the do-it-yourselfer.

T. Lewis

Offline "Cadillac Kid" Greg Surfas 15364

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Re: r134a conversion
« Reply #9 on: March 27, 2012, 07:41:48 AM »
All that is required to obtain your refrigerant license is taking the tests that certify your understanding of refrigerants any your legal responsibilities in handling them.  What is "around the corner" is the extreme restriction on the sale of R-134a because of it's phase out and replacement with HFO-1234yf.  R-22, the refrigerant used for decades in commercial and Home Air Conditioning units is currently being phased out, and the price of a 30# drum has more than tripled.
Greg Surfas
Cadillac Kid-Greg Surfas
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-

Offline pauldridge

  • Posts: 265
  • Phil Auldridge
  • Name: Phil Auldridge
A/C Technician Certification
« Reply #10 on: March 29, 2012, 07:44:02 PM »
Greg,

You're absolutely right about the ease of obtaining a Motor Vehicle A/C Technician Certification.  I've installed a number of systems on my own cars, and hear the rumors about even R-134a possibly not being available over the counter in the near future.  I did an internet search and found, as you've mentioned, it is merely a matter of taking an online written test to obtain your permanent MVAC certification.  As I recall, the cost was less than $50.  It's an open book test (they provide you the reference material), and took me about 1.5 hours to complete.

Gosh, a few months ago I couldn't even spell A/C technician, and now I ARE one, complete with  plastic EPA certification card!

There are lots of companies online that administer these tests.  The one I used can be found at: http://qwik.com/education-and-training/
Phil Auldridge
Austin, TX
1940 60S as well as MGA, Stingray, '39 Ford Coupe, BMW 3.0 CS, '59 Jaguar, '51 Hudson Hornet, '64 and '70 Mercedes roadsters, and Nash-Healey LeMans Coupe

Offline Art Director

  • Posts: 204
  • CLC Member #11513
  • Name: Tim Coy
Re: r134a conversion
« Reply #11 on: March 30, 2012, 12:09:53 PM »
Wow, thanks for the education on A/C, especially our resident expert Greg Surfas. I look forward to attending his seminar at the St. Augustine Grand National.

Just completed a restoration on my 1963 Sedan de Ville and had the choice to stay with R-12 or convert to R-134a. Now with this news, I'm glad I chose to stay with R-12.

Tim
Tim Coy
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Offline waterzap

  • Posts: 767
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  • Name: Waldo Du Toit
Re: r134a conversion
« Reply #12 on: March 30, 2012, 12:41:17 PM »
Is that the EPA 609 Technician Certification ?
Charlotte, NC
-1978 Eldorado Coupe

Offline bcroe

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r134a conversion
« Reply #13 on: March 30, 2012, 04:05:02 PM »
You can replace R12 with a propane butane mixture for a song, need less than 2 lbs.  Bruce Roe

Offline waterzap

  • Posts: 767
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  • Name: Waldo Du Toit
Re: r134a conversion
« Reply #14 on: March 30, 2012, 09:19:16 PM »
You can replace R12 with a propane butane mixture for a song, need less than 2 lbs.  Bruce Roe

Very nice, thanks Bruce. Just doing some research now. Found this article

http://www.hychill.com.au/pdf/hcramcac.pdf

Am I correct in that you can use LPG or Propane,  which is LPG without the Butane?
« Last Edit: March 30, 2012, 09:49:49 PM by waterzap »
Charlotte, NC
-1978 Eldorado Coupe

Offline bcroe

  • Posts: 749
    • CLC Member
      CLC Member #14630
r134a conversion
« Reply #15 on: March 31, 2012, 10:01:32 PM »
I had this done to a car on my last visit to Canada, by a Cad owner & chemical
engineer.  It worked fine, gas is gone now.  I haven't learned to do it myself
YET, but wait till I run out of R12.  Can't answer any tough questions about
it right now.  Bruce Roe

 



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