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  • njboy
    replied
    Originally posted by blyguy View Post
    . Then, pull a vacuum at a shop and fill with R134 with fingers crossed.

    Cheers
    Bryant
    I wanted to pull a vacuum but couldn't find a shop in my area that wanted to work on an R12 system. They all said that they either didn't want to risk contamination or flatly refused to work on it. Does anyone else encounter this problem.

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  • blyguy
    replied
    Good point John, I think changing out all the o rings, flushing the condensor and evaporator are pretty labor intensive jobs just to switch to R134. If someone had a decently functioning R12 system, it seems more reasonable to keep that running with Freeze 12 or R12.

    I've read that changing out the o-rings is not necessary for switching to R134, as the only difference is the heat resistance between the rubber material. I believe my car has been switched over the R134 already, so I'll be trying to get it running by checking for leaks, check the compressor clutch, hi/lo switches, and coolant temp sensor. Then, pull a vacuum at a shop and fill with R134 with fingers crossed.

    Cheers
    Bryant

    Leave a comment:


  • 02fanatic
    replied
    Originally posted by blyguy View Post
    This is from the SIG archives - James Muskopf gets all the credit. Some highlights:

    R134 charge is about 80% the weight of the R12 charge

    Monitor your A/C vent temp with max A/C, fan on 4, windows open - the high side pressure (in psi) should be 2.3 times the ambient temperature (in deg F). The low side pressure should be > 20 psi.

    I'm going to give this procedure a try in the near future and keep you all posted.

    Eric
    That's good information. Thanks for the A/C forum link also. I'd be interested in seeing what pressures the R134a end up being in a well functioning system in an E30 M3. Please post back your results.

    It's still alot of work swapping to R134a though.....I don't see the need for that as long as the stock system works adequately.

    John
    Last edited by 02fanatic; 07-20-2010, 07:26 AM.

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  • mtony
    replied
    Wow, thanks blyguy! I think I'll try to get my A/C recharged this evening.

    Leave a comment:


  • njboy
    replied
    Blyguy thanks for that write up. A couple of things that I didn't do that you had in your write up and that was I didn't clean out the condenser or pull a vacuum on my system. I was aware that moisture getting in is bad so I worked quickly putting everything back together. I put two cans of R134 in and the system works well. I'm sure pulling a vacuum will get air and moisture out of the system and I'm sure the system will run more efficiently but in my case it still works quite well without doing a vacuum pull. I would recommend that one still follow the complete directions just in case how I did it has an effect on system longevity.

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  • Emdrie
    replied
    whoa! now that's a robust answer to the question haha

    Leave a comment:


  • blyguy
    replied
    This is from the SIG archives - James Muskopf gets all the credit. Some highlights:

    R134 charge is about 80% the weight of the R12 charge

    Monitor your A/C vent temp with max A/C, fan on 4, windows open - the high side pressure (in psi) should be 2.3 times the ambient temperature (in deg F). The low side pressure should be > 20 psi.

    I'm going to give this procedure a try in the near future and keep you all posted.

    To: E30M3List
    Subject: Re: [M3] A/C Hi and Lo pressure question.
    From: James Muskopf
    Date: Wed, 11 Jul 2001 05:50:22 -0700 (PDT)

    Everyone with A/C questions needs to visit the air conditioning
    board:

    http://www.aircondition.com/wwwboard/

    Browse the messages. The ones that have the most detail are the ones
    that get the best responses (kinda like this mail group).

    To convert from R-12 to R-134a, you should remove and drain the
    compressor (measure the amount oil you remove), run the pump by hand
    to assist in draining out as much of the mineral oil as possible,
    refill with the proper amount of Polyalpha+ oil (brand name that
    mixes with any refrigerant or oil). Remove the condensor and all
    accessable lines. Flush those with Brake cleaner and clean
    compressed air (make sure it doesn't spit air-tool oil into the
    lines. Clean the bugs out of the condensor, and wash it with a good
    degreaser. www.acsource.com sells all kinds of cool A/C stuff, like
    the Poyalpha+ oil, gauges, conversion kits, o-ring assorments, and
    Nylog--an o-ring seal/lubricant. Buy everything from there. They
    have the best assortment and prices I've found. You will NOT find
    anyone at parts stores who has more than just a casual knowledge of
    A/C systems. I've looked around. Don't waste your time at local
    shops.

    Removing the A/C evaporator (under the dash) isn't that hard. NOT
    TRUE on the E28--it took me 2 days. Remove, flush, and replace.
    This is important to prevent excess mineral oil (from the R-12
    system) possibly screwing up your R-134a system.

    Replace the expansion valve with one suitable for R-134a. I think
    all new expansion valves are R-134a compatible. Get all new o-rings
    for anything you dismantle--an assortment pack is the best way to go.
    I paid too much for an R134a conversion kit that came with oil and
    o-rings. You should just buy an o-ring assorment vs. individual
    rings from the dealer. You will have to measure individual
    rings--the CD only lists them by size, not by location, and you'll
    spend $35 on a dozen o-rings vs $50 on a hundred. Sell the kit when
    you're done.

    Also, you MUST replace the drier with one suitable for R-134a (X-7 or
    X-9). Old R-12 driers are probably saturated with moisture and crud,
    and they are not expensive. Whenever you open the system for
    repairs, ALWAYS replace the drier. I believe all new driers are
    R-134a compatible.

    Then you have to put everything together. Use Nylog on all the
    o-rings and flare-nut threads. Do not open the drier until the last
    moment before you install it--it absorbs moisture from the air as it
    sits open.

    You have gauges? Do they fit R-134 fittings or R-12 fittings? It
    doesn't matter, just make sure they are accurate and you have all the
    R-134a can tap and any adapters necessary. You can buy a conversion
    kit to fit R-134a fittings onto R12 gauges for about $35. Mine came
    with the R-134a fittings for the car, adapter hoses, a can of R-134a
    oil, and other assorted R-12 to R-134a fittings.

    Then get your handy-dandy vacuum pump. Don't have one? Well, you
    can then go to a shop and fork out $50-150 for them to pull a vacuum
    for an hour or so. Or you can see if the local tool-rental place
    rents A/C vacuum pumps. Pull a vacuum for about 30 minutes with a
    dedicated vacuum gauge. Some pumps already have a gauge. I say
    dedicated, because a combo vacuum/pressure gauge only has a very
    small arc for its vacuum readings--very low resolution. Put your
    gauges on the system, too. You don't want to take 2 hours pulling a
    vacuum and then introduce air when you put the gauges on! Also, you
    should pull the vacuum from the high and low sies at the same
    time--open both valves on your gauges. After 30 minutes, turn off
    the vacuum pump and watch it for another 20 minutes. The vacuum will
    drop by 0.5 inHg or so because of moisture boiling off. Turn the
    pump on for another 30-60 minutes for good measure.

    Then when you're done, remove the pump and fit the R-134a and
    can-tap. Crack open the valve to purge the air from the line, then
    fit the line to the gauges. Open the can valve, and open the LOW
    SIDE only. Let it suck a can of R-134a into the system. Total
    R-134a charge should be 80% of the spec R-12 charge (by weight).
    Advice from the A/C board was to fill near the correct charge, start
    the car and run the A/C with a thermometer in the vent. Your high
    side pressure (psi) should be about 2.3x the ambient air temp (deg
    F). Very slowly add while monitoring the vent temps with the windows
    down and A/C on max, fan on high. Do not exceed 2.5 times the
    ambient. Low side should not drop below 20psi, should run about
    20-25psi when the compressor is on.

    Once you've spent all this friggin time and a hundred or so bucks,
    you'll have cool A/C. If you want it to work, this is the ONLY way
    to do it right.

    James Muskopf
    [email protected]

    --- eric_m3 wrote:
    > What should the High And low pressure readings be when I recharge
    > my A/C system w/ R134?
    >
    > Will I need to change O-rings or fittings for this conversion?
    >
    > I am getting different opinions so some clarification would be
    > helpful.
    >
    > Eric

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  • 02fanatic
    replied
    Originally posted by mtony View Post
    Does anyone know what low and high side pressures a system running R-134a should have and how they would compare to a system with R-12?
    Good question! I only had a Haynes A/C Manual to work with and the spec pressures for R12 were rather generic depending on model year, but I am running about 35psi (low) and 190psi (high), give or take 5psi...that's with Freeze 12. I believe that's in the ball park....ambient temp and altitude can affect operating pressures as well.

    Typically R134a operates at a higher pressure, but it also can require "more volume", which may affect pressure, especially on a retrofitted vehicle. This is why larger condensors are often recommended when converting from R12 to R134a.

    I don't have any experience with R134a in an E30 M3...would be interesting to hear input from someone running R134a.

    Leave a comment:


  • mtony
    replied
    Does anyone know what low and high side pressures a system running R-134a should have and how they would compare to a system with R-12?
    Last edited by mtony; 07-19-2010, 03:05 PM.

    Leave a comment:


  • 02fanatic
    replied
    Originally posted by njboy View Post
    Even though Freeze12 is not banned by the EPA it is still bad for the ozone layer. I just found an old can of it that I used years ago and it says that this product is not good for the ozone layer right on the label.
    I did the conversion to R134 this spring and the system (knock on wood) is doing well during this heat wave in the North East. Replace the oil with PAG or a compatible Ester oil, new dryer and sensor with new o-rings. Refill and enjoy. Really not that bad of a job. Hardest part is removing the compressor to drain its old oil.
    No refrigerants are "good" for the ozone layer, "including" R134a....only problem with R12 is it leaks through hoses & fittings (especially when the A/C is not maintained & used regularly)....R134a uses hoses that protect against such transmission. It's a fact that R12 and R12 alternatives operate at much lower pressures than R134a (especially Freeze 12 and others)....that's for me until I have no other choice but to swap everything out. If and when a major A/C system component fails - like the compressor, expansion valve, or evaporator (and my system needs to be opened up and serviced throughout) I may go with R134a or other (as time marches on), but not now. If it's not broke don't fix it!
    Last edited by 02fanatic; 07-16-2010, 06:18 AM.

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  • njboy
    replied
    Even though Freeze12 is not banned by the EPA it is still bad for the ozone layer. I just found an old can of it that I used years ago and it says that this product is not good for the ozone layer right on the label.
    I did the conversion to R134 this spring and the system (knock on wood) is doing well during this heat wave in the North East. Replace the oil with PAG or a compatible Ester oil, new dryer and sensor with new o-rings. Refill and enjoy. Really not that bad of a job. Hardest part is removing the compressor to drain its old oil.

    Leave a comment:


  • Ryan M
    replied
    Thanks for the update. Need to address this when I put my car back together. Will have to look at the Freeze 12.

    Leave a comment:


  • 02fanatic
    replied
    Originally posted by JackinMidtown View Post
    I'm not doing the conversion. My shop uses the Freeze 12 and says that it works just fine. But, still got to get that new **** compressor. I typed the wrong "co..." word in the previous post. There are no compressors available through BMW right now.
    Jack,

    Please let me know how your charge with Freeze 12 goes.

    FWIW, I was successful charging my system with Freeze 12, after "much" research on A/C systems, fittings, vacuum pumps, gauges, low/high-side pressures, etc. Hans "blows cold" A/C now!

    John

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  • Mdriver
    replied
    I stuck with the R12 when i found my AC leak last year. I like ice cold air in SoCal.


    - gabor

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  • 02fanatic
    replied
    Originally posted by Eric Giles View Post
    I'm personally not sold on Freeze 12, so I have stuck with r12 on my two E30's. You can sometimes buy cans of r12 on ebay for around $20-25 a can plus shipping, which is really not a lot more expensive than r134a or Freeze 12. As was mentioned, the condenser on our cars really isn't large enough for r134a to cool as well as it could. Plus, if I am not mistaken the seals in the original compressors used in the M3 aren't compatible with the oil used in r134a.

    One drawback is that you cannot get (to my knowledge) an r12 specific expansion valve for an E30 anymore. The r12 part has been replaced by BMW parts with a r134a/r12 'compatible' valve that does not work as well with r12. When I fixed the a/c on my '88 M3 four years ago, I was able to get an r12 specific expansion valve and that system works perfectly. However, in my current E30, I am having to use the r134a valve and it doesn't work as well as it should. This has been verified by others that have had the same results and by an a/c technician. It really only affects cooling at idle, but still it is a small drawback. There is a writeup on E30tech.com on how to refurbish the original r12 expansion valve so that is what I would do if someone was to stick with r12.

    Just throwing another opinion out there...
    Thanks Eric....good info. I am in the same area of thought as you, since I refurbished my R12 system on the M5 in the 90's...of course R12 was more available then than now, but it was still expensive.....I chose to stick with R12.

    One issue I "do have" with R12 is the leaking of freon through the lines when the system isn't used very often. I think Freeze 12 may be a viable option for those of us who don't want to convert to R134A and who have cars that sit alot. Freon (R12) just isn't a realistic option any longer in that situation IMO. If I drove the car more, R12 would be a definite for me now, as long as the compressor and other system components are still functional.

    I'll post a follow-up on the resluts of my troubleshooting my E30 M3's system and the use of Freeze 12..it might take me awhile, but I'll get there eventually. If I want my wife to accompany me to M3 gatherings I "HAVE TO" get the A/C working!:gotcha:

    John

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