R12 to R134a RETROFIT
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, R12 to R134a RETROFIT in Past Cadillac Vehicle Discussion; I own a 1991 Sedan Deville that I love more than my wife and kids [well....at least my wife]. The ...
  1. #1
    D4262 is offline Cadillac Owners Member
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    R12 to R134a RETROFIT

    I own a 1991 Sedan Deville that I love more than my wife and kids [well....at least my wife]. The R12 AC system has a very minor leak to were the compressor has shut down via the F47 code.

    Rather than trying to find some R12 and topping-out, I would like to convert to a R134a Retrofit. However, I've read where a conversion on 88-93 Caddy's is a problem because of the low temperature evaporator sensor.

    Has anyone here done a SUCCESSFUL conversion that has lasted a couple years and tell me what steps I need to follow to accomplish the same?

    Thank You
    Carl

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  3. #2
    Anthony Cipriano is offline Cadillac Owners Fanatic
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    Re: R12 to R134a RETROFIT

    There should be no problem converting to R134a. I converted a friend's 90 deville to R134a and it's run fine now for 3 years. He lives in South Florida so the system gets a work out and has plenty of capacity.

    The real key to success is to make sure the system is cleaned of as much of the old oil and purged of R12. The accumulator must be replaced to get a fresh dessicant charge in the system. This is the part that is most often skipped and causes problems as the R134a will not operate at maximum efficiency if there is not a fresh dessicant charge in the system. Charge the system to the same charge as was specified for R12. Do not be tempted or convinced to charge to a lesser amount due to some ficticious R134a "conversion" factor. Use the correct charge for R12. If done this way the system will cool fine and will not set any low refrigerant codes. The diagnostics will work fine with the R134a if it is charged correctly.

    It is a good idea to remove the compressor if possible to drain as much oil from it as possible. Disconnect the lines and purge the system with air and a solvent if you have away of dispensing and catching it and drying the system with an adequate source of air.

    If you have a leak now you will really have a leak with R134a. It does tend to leak more and exacerbate any existing leaks. It will be easy to top the sytem off occasionally but you will have to do it much more often. It would be best to find and fix the leak before converting.

    Spend the extra money for the GM conversion parts. The conversion fittings for the fill ports will not leak. Many of the cheaper aftermarket parts will leak. Forget the cheapie conversion kits. Sure death to the system.

    You have to use the correct PAG oil with the R134a as the conventional mineral oil used with R12 is not compatible at all with R134a. That is why it is necessary to get as much of the old oil out of the system and then install the correct amount of the PAG oil that is compatible with R134a.

    Even a tight system will tend to loose a little charge with R134a. Later model cars equipped with R134a from the factory had slightly different hose materials and fittings as the R134a has a greater propensity to leak due to the smaller molecule size. You should be fine with a 91 system that is intact and in good shape (aside from the leak you know about) but be aware that you may need to add a can of R134a once a year or so.

    With the correct oil there should be no reliability problems at all with the R134a conversion. The system will have virtually the same cooling capacity with R134a as it did with R12 if you get the new accumulator in the system and charge to the correct level.

  4. #3
    D4262 is offline Cadillac Owners Member
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    Re: R12 to R134a RETROFIT

    Thanks for the info, Anthony.

    Would you or someone else here know how many ounces of freon and oil this '91 system holds?

  5. #4
    N0DIH's Avatar
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    Re: R12 to R134a RETROFIT

    I converted my 91 over with a Walmart $30 kit. Works fine, but the quality of the fittings is poor, they work, but far from what I would call GM Quality. I have done a couple other cars also, no issues. (2 Aerostar Vans, 1 91 Bonneville, 1 91 Cadillac). No issues to date. Ensure you have fill kits with BRASS fittings, not platic. I got a face full of oily R134a. I wasn't amused. Glad I had glasses on.

    I have a high/low pressure gage and a low pressure gage, so I am able to charge to actual pressures as opposed to weight only. Use the weight for actual amount, and then monitor pressures based on temp. (Meijers has a $20 high/low pressure gage that you can connect to either side)

    Mine has only been converted for a few months, but it is flat out frigid, something I didn't expect from R134a. I do miss my R12.

    Did I swap the accumulator? No, would like to, but $$......... The issue with the accumulator is it holds some of the R12 oil. You won't get it out (well, maybe if you are nutty enough to run a solvent through the system to clean it out, which if you have a compressor failure, DO!). Supposedly the new oil with the retrofit kits is compatible with the R12 oil. I don't honestly know, but mine works fine and isn't grossly leaking.

    Take Anthony's advice, swap the accumulator, use GM Retofit parts and enjoy years of COLD air! Vacuum it down first to ensure ALL moisture is out. If you are having problems vacuuming it down past a certain point you have moisture in the system. Once it is out you will be able to continue dropping the pressure. I use a modified R12 filler connected to a vacuum tee and my vacuum pump (hand operated), I connect 1 line to the engine to pull it down to 20 inches or so, go drive it for a 1/2 or or so, pinch the line, and start pumping and pumping and pumping....

    Oh, and if they insist you swap compressors, don't waste the $$, in most cases they are IDENTICAL P/N Compressors. The only things that are different are the pressure switches, those should be swapped, but..... Make sure you have the oil in there though, or you WILL be swapping compressors!!!

    Tom

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    Re: R12 to R134a RETROFIT

    like Tom said, you need to pull a vaccum...

    where can you get the correct tools to do that? I remember with my Olds, the AC never worked, so my father converted it for me... we didn't change anything at all, but he got the machine on it and pulled a vaccum... he said that is the part that people leave out when they do those quick kits... the AC system in the Olds held to 5 microns I believe... it was very good, and no leaks.. the car sat for 1.5 years before I bought it, that is probably why it wasn't working.... after that we filled it up, although I don't think it is filled all the way.... it dosn't blow ice cold... as the hottest summer days I gotta keep it on max and high and stuff, but for the most part, it works fine... much better then not working at all.....

    ... the '93 was slightly low on R12 (didin't throw the code though) so we topped that off with R12

    when I bought the '79 the guy said there is a leak around the compressor, and the AC dosn't work at all... one day I would like to get it working again... everything is there...

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    Re: R12 to R134a RETROFIT

    I haven't found a pump yet, other than the engine itself (great vacuum pump!!!). I did mine to pull to around 20-21 inches then pulled it by hand pump to 26-27. My hand was in pain by then, so I said nuts to it....

    Just get an extra hose from one of the kits (I have bought a couple of ther years), hack off the can end, and splice in a vacuum tee and connect it to the engine, and then port off another to a hand vacuum pump. Just pinch the hose to disconnect the engine and pump away. Then release the quick connect from the engine and connect up a freon can.....

    I would guess JC Whitney would have them. Or if you have a compressor for air can you tap off the intake and seal it off? Don't know, don't have one...

    Tom

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    D4262 is offline Cadillac Owners Member
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    Re: R12 to R134a RETROFIT

    Hey 'Tom'
    Is that '91 Deville the one you got from your dad?

    I'm impressed with your ingenuity and imagination. That vacuum pump idea using the engine intrigued me, however, I will probably just rent one at the local 'Rent All' place for $25.00 a day --- just to do it right.

    I'm still concerned about 'Anthony Cipriano' suggestion about charging with the SAME amount of 134a vs. R12. Everything I've read on the 'Net' about doing conversions says to use LESS 134a due to the difference in pressure of the two refrigerents. There seem to be a lot of contrary opinions floating around in respect to doing these conversions.

    Carl

    P.S. '91 Deville AC system holds 38oz R12

  9. #8
    Anthony Cipriano is offline Cadillac Owners Fanatic
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    Re: R12 to R134a RETROFIT

    The GM HVAC engineers that developed the systems for R12 and R134a recommend that systems that are converted from R12 to R134a should be charged to the same capacity with R134a as they were specified for with R12. I've worked on several of them.

    If you'd rather trust the internet experts then charge it to a lower level and then when it doesn't cool as well as you would expect and/or repeatedly sets the "low refrigerant" codes you can add the remainder to the same charge as was specified for R12 and find out for yourself. Save yourself the trouble and charge to the correct level as was specified for R12. The low refrigerant detection codes that the systems use require the correct charge level. There are numerous service bulletines from GM regarding converting R12 systems to R134a and they recommend charging to the correct level as was spec'd for R12. GM understands their systems better than the internet experts. Besides, what harm do you suspect could come from "overcharging" if the system really needed less R134a?

  10. #9
    D4262 is offline Cadillac Owners Member
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    Re: R12 to R134a RETROFIT

    'Anthony Cipriano'

    It was NOT my intention to offend you by questioning your recommendation.
    However, it is in my nature to question everything especially when there are conflicting views presented. Please note the statement below with link included.

    General Motors Retrofit Procedures
    REFRIGERANT REPLACEMENT FOR R12
    R134a as the only substitute for R12 refrigerant that GM recommends. Recharge the system with about 15% less R134a than the R12 specification. Their formula is: (R12 lbs x .9) - .25 lb. = R134a Charge

    http://www.delanet.com/~pparish/gm-rp.htm

    ================================================== =======

    You wrote
    "There are numerous service bulletines from GM regarding converting R12 systems to R134a "

    Please be so good as to furnish me with a link where I might find that information.

    Thanks
    Carl

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    Ray89 is offline Cadillac Owners Member
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    Re: R12 to R134a RETROFIT

    Changed my 89 Allante about three years ago and it works good. I took mine to an A/C shop and they did the conversion for $125. The shop replaced all the necessary items to make the conversion properly. Cant tell you what these items were, but I saw them to verify they were installed. Ray89

  12. #11
    Anthony Cipriano is offline Cadillac Owners Fanatic
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    Re: R12 to R134a RETROFIT

    Several of the Allantes that were converted to R134a set the "low refrigerant" code when charged according to the "R134a conversion" recommendations. They quite setting the code when the charge was increased to the same charge was was specified for R12.

    My father's car was charged to the same level with R134a as was spec'd for the R12 and it works great and does not set any codes. Possibly the idea to lower the R134a charge started because the R134a systems tend to run a little higher head pressure than they did with R12. In a perceived need to lower the head pressure the charge was reduced and someone thought this was the correct thing to do. It isn't.

  13. #12
    N0DIH's Avatar
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    Re: R12 to R134a RETROFIT

    Quote Originally Posted by D4262
    Hey 'Tom'
    Is that '91 Deville the one you got from your dad?
    Yup, love the car. They bought a 97 Cadillac in 97, and have it, and the 91 got most of the miles and the 97 got to sit and only get taken on trips. Then they bought an RV so they needed a Saturn to pull (towbar, on all 4 wheels, Cad can't). So I was able to get the 91. Love the car, runs great, gets good mileage, especially for a V8, looks great and has awesome power.

    My mom and dad miss the low end power in the 91 on the 97. But on the highway, the 97 does better. Mileage is close to the same both cars. When I told my dad the 94's could be had with the 4.9 or N*, he was interested.... Maybe when the Saturn goes down the road a Cad 4.9L will grace the garage again!

    Tom

  14. #13
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    Re: R12 to R134a RETROFIT

    Mine was converted 5 yrs ago and it runs cooler then both our newer cars.....but I like windows down better.

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    SeanHarrington is offline Cadillac Owners Member
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    Re: R12 to R134a RETROFIT

    Silly question, how can I tell, by looking at the fittings, if my 93 deVille has been changed over to the R134 system? I know lots of AC work was done 3 yrs ago, new compressor atleast, and now the AC light is on, and no cold air.

    I was told the fittings for the refrigerant are much bigger, and the plastic caps are really huge, it it has been changed. I'd really like to see a photo on the web!

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    Re: R12 to R134a RETROFIT

    R12 fittings are externally threaded much like a tire valve. R134a fittings are quick disconnect type, similar to what you wouls find on an air compressor.

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