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A/C Problems

Discussion in 'The Garage' started by cbbr, Mar 25, 2005.

  1. cbbr

    cbbr 1 ton status GMOTM Winner

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    Air worked great for about three days after I bought my 90 'Burb. Then it died. Specifically, the compressor (R-12) died.

    I replaced the compressor and filled the system with R-34 b/c the R-12 is so expnsive. I also replaced the accumulator (I think that's what its called).

    The front air blows cool, but not cold like it did before. I wrote this off to the R-34 instead of R-12.

    The rear air, which was not touched in the process, blows hot. It blows, just is not getting cool at all. Its 85 degrees today and takes a long time to get the 'Burb to cool down.

    Anyone have any idea what may be causing the rear A/C to be out? While on the topic, any idea how to make the front A/C cooler.
     
  2. BobK

    BobK 1/2 ton status

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    Did you evacuate the system before adding the R-134?
    If the syatem was not evacuated there is air and water vapore in the system.Air and water vapore in an A/C system will render the A/C almost useless.

    You can't just add R-134 to a R-12 system.The cooling properties of R-12 are very different than R-134.
     
  3. cbbr

    cbbr 1 ton status GMOTM Winner

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    The R-12 all leaked out when the compressor gave up. I hooked up a vaccum to several system lines when I changed the compressor and thought that I had it cleaned out.

    Is there a specific line that needs to be vaccumed?

    Also, are there filters in that system that need to be changed? I asked at the time that I changed the compressor, but the parts guy said no. Experiance with other things (that I know something about) has shown that he dosen't always know what he is talking about.
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Both the front and rear air operate from the same compressor and freon, so working on one will affect both.

    As for the vacuum work... You need to pull a vacuum on the entire system, not vacuum out the lines. Once you have replaced the defective components and the system is sealed up, you have to attach a good vacuum pump and let it suck all of the air and moisture out of the entire system. It usually takes about an hour and will pull down to around 29 inches of vacuum. :eek: Then you can start replacing the freon. When you convert a system from R12 to R134, you have to use more R134 than the R12 system required. I don't recall the exact calculation, but it should be pretty easy to find using Google.

    R134 is also very sensitive to having just the right amount of freon. Just a little too much or too little and you will get poor cooling.
     
  5. BobK

    BobK 1/2 ton status

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    As harry said.Once the system is all sealed up again you need to pull a vacume for at least an hr.With a large system like the burb has,the longer the better.

    You need a vacume pump something like this to do the proper job.
    [​IMG]
    Also to properly convert to R134 the system needs to be flushed out ridding the system of the r-12 oil(mineral oil).All the o-rings should be replaced,replace the acumulator/dryer,expansion valve or orafice tube,and replace any hoses that may have a muffler or filter inline.All these compnents will have the old R-12 oil in them and are unflushable.

    Here is a link for the minimum requierment for converting to R-134.
    HERE

    Switching over to R-134 is much more involved than it seems.
     
  6. cbbr

    cbbr 1 ton status GMOTM Winner

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    I never realized that over charging might pose a problem. Live and learn. I did the conversion before becomming a member here and with "help" from a friend.

    I am sure that we overcharged it as we just kept putting 134 in until it got cold and then kept putting it in b/c it was not getting cold enough.

    Maybe I need to drain/vaccum the system and recharge???
     
  7. r_pogo

    r_pogo Registered Member

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    Blends?

    Do a Google on:

    Free Zone (RB-276), Freeze 12, Frigic (FR-12), Autofrost, McCool Chillit, Hot Shot, Kar Kool.

    Also search ackits.com for "Arizona Moblie Air Test Laboratory Division Various Performance Tests Alternative Refrigerants and Oils" (PDF)

    Also see www.hostingprod.com@aa1car.com/library/tr497.htm

    Blends are a combination of refrigerants to replace R12. Tests show that some of these blends cool better at lower pressure than straight R134A and are more compatible with R12 systems.

    Bottom line:

    1) Don't believe all the blend advertising claims.

    2) Reading the fine print: you still have to change out all the rubber parts (o-rings & seals) and dryers for those blends that include some R134A.

    3) For some blends you don't need to completely clean out the mineral oil but still need to add some R134A type oil for best results.

    4) Pressures are generally lower than straight R134a, about the same as R12 which is much better for older systesm.

    5) Cooling is better than R134a with some blends, comparable to R12.

    6.) Most AC shops won't touch the stuff since they need a dedicated recovery system for each blend and will not likely make the investment. Don't count on any help from them.

    I have not tried this stuff myself but have an 87 Chev that needs a new compressor so something will have to be done before long (Arizona).
     
  8. gone huntin

    gone huntin 1/2 ton status Premium Member

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    You definately need to replace your orifice tube, it'll probably be covered with metal from the old compressor.
     
  9. cbbr

    cbbr 1 ton status GMOTM Winner

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    Newbie question, but where is it and what does it look like?
     
  10. BobK

    BobK 1/2 ton status

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    This is a fixed orafice tube(FOT),the blue plastic thing.This is a Ford FOT,GM FOT's are white.
    [​IMG]


    Where it is located on your year vehicle I'm not sure.Sorry.
     
  11. cbbr

    cbbr 1 ton status GMOTM Winner

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    Anybody tell me where the orrifice tube is?
     

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