Can I use R134 to "test" R12 system for leaks?

Discussion in 'The Big Chill' started by ranger, May 17, 2012.

  1. ranger

    ranger Well-Known Member

    Hi folks,

    Got a leak in my '70 lark. I suspect it is a Schrader valve. I've got plenty of original R-12 but don't want to waste it for testing. Can I shoot some R134 in there (and NOT turn on the compressor) just to find my leak, or will that pollute the original oil in the compressor and the system.

    I have coverted over several R-12 cars to R-134 and they do NOT cool as well/quickly.

    Thanks!

    Best,

    Ranger
    Aiken, SC
     
  2. lsrx101

    lsrx101 Well-Known Member

    Yes, you can do that.
    Pull a hard vacuum then add R134a until the system and container equalize in pressure. You can even add nitrogen, or even dry compressed air in a pinch, to raise the pressure in the system to about 125 psi or so.
    Then go to to it with your sniffer, soap bubble mixture or other favorite detection method.
    Just give it an hour on so on the vacuum pump before charging with R12.

    Do change the receiver/dryer if it's more than a few years old. It's a wear item and now is the perfect time to change it.
     
  3. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    back when I did some AC work, it was a normal practice to fill the system with normal shop air to find a leak. I wouldn't use 134, its kinda pricey to waste like that..
     
  4. Briz

    Briz Platinum Level Contributor

    NO!!! Never mix or "blend" refrigerants. Use nitrogen or shop air if you must. The oils in the 134 are not compatible with the 12. even if you vacuum out the system there will still be oil in there. If you don't have the correct tools don't do the work.
     
  5. ranger

    ranger Well-Known Member

    Hi folks,

    Thanks for the (disparate) replies.

    1. How do you insert compressed air into the system? In effect, what type of adapter do you use on your air guy that allows you to hook it up to R-12 manifold gauges? As well, I agree that the air should be dry and filtered, so I would use one of those filters right in front of the air gun--the type that painters use before their spray guys.

    2. Keep in mind I wasn't talking about turning the compressor on with the R-134 in there, so would it still contaminate the R-12 oil?

    3. I don't care about wasting the R-134; one or two cans should suffice at about $12.00/can, last I checked.

    4. NOBODY around here has the "correct equipment to do the job." They would need a charge cylinder of R-12, insert it and the dye in the system, and then evacuate the R-12 back into their recovery cylinder. Shops, at least around here, do not deal with, or have any use, for R-12. I have plenty of it, but don't have a recovery system and sure don't want to waste it.

    5. Of course, I would change the accumulator and orifice tube at this time. I have already purchased both from the GM dealer.

    So, now I don't know what to do--insert the R134 or not. I guess I will have to do more research.

    Thanks, again.

    Best,

    Ranger
    Aiken, SC
     
  6. dynaflow

    dynaflow shiftless...

    Yes...oil distributed throughout entire system...

    Nitrogen can be used for leak testing...
     
  7. BUICKRAT

    BUICKRAT Torque Rules!

    As long as the 134 does not contain oil, you will be ok. Problem is, most of the small recharge cans have oil and dye in them, so if thats what you have, don't do it. If you have pure 134 in the 30 lb containers, go right ahead. The problem with shop air is the molecules are larger than refrigerant and may not show a leak. Problem with 134 is the molecules are smaller than 12, so you may find yourself chasing leaks that don't matter. Good Luck!
     
  8. ranger

    ranger Well-Known Member

    Hi folks,

    thanks again for taking the time to reply.

    John, how do I inject nitrogen into the system (sort of the same question as how do I inject shop air into the sytem (an issue of adapters).

    And, where do I buy nitrogen (in small quantities)?

    One more thing (for everybody); I think I have a leak at the Schrader valve on the low side. Are these valves the same as tire valves or are they diffferent?

    Thanks, again!

    Best,

    Ranger
    Aiken, SC
     
  9. dynaflow

    dynaflow shiftless...

    Nitrogen in container under pressure...inject as you would freon...

    Available from welding suppliers....

    We're beginning to get far afield here...considering value of your R12, nitrogen equipment costs, etc...maybe just let a/c shop find leak and afterwards you keep system charged w/your R12 supply...
     
  10. 71skylark3504v

    71skylark3504v Goin' Fast In Luxury!

    What the heck are you talking about? No one is mixing anything. He's just using 134 to pressurize the system. Not a bad idea, if you don't have anything else, and it will show up with a sniffer.

    Definitely make sure if you use a can of 134 that it contains NO OIL, and evacuate throughly.

    Correct tools are always nice, but if you don't have them you just have to make do. Exactly why the I've opened the A/C system up in my Ranger twice now and have never vacuumed it down, but it cools as good as ever.
     
  11. lsrx101

    lsrx101 Well-Known Member

    NO!!! Never mix or "blend" refrigerants. Use nitrogen or shop air if you must. The oils in the 134 are not compatible with the 12. even if you vacuum out the system there will still be oil in there. If you don't have the correct tools don't do the work.

    Briz, all of your points are very much valid. However, your concern about "oils" is valid if using "R134a containing oil or???" I should have been more specific in my reply.
    You can use "VIRGIN" R134a for leak testing. NO OIL OR ADDITIVES.
    Its usually located on the bottom shelf and will seldom (never?) have a "charging hose" attached. You need a proper can tap and manifold gauge set to use it.
    Also, shop air used for testing must be BODY SHOP DRY. Moisture from the direct output of a compressor can quickly saturate the desicant in an accumulator or receiver/dryer. Using compressed air for pressurizing the system is actually a big red flag among AC pros.

    70Skylark3504v,
    Correct tools are always nice, but if you don't have them you just have to make do. Exactly why the I've opened the A/C system up in my Ranger twice now and have never vacuumed it down, but it cools as good as ever.
    You've gotten lucky with your Ranger, and I wonder about long term reliability of the compressor.
    Many folks don't get that lucky and I make a lot of money off of their lack of tools/knowledge. I have a conscience and hate dealing with those situations.
    I would much rather advise people of the "right" way to do the repair with the proper tools than make money from simple, cheap repairs that failed and became big ticket repairs when they followed your example.
    "Making do" will seldom give good, long term results when dealing with an automotive AC system. How long or how good is a crap shoot, at best. When "making do" doesn't work, the price of the repair often increases by a factor of 20 or more.
    There are certain shortcuts that you can take, but there are also certain tools that are "must have" to do it DIY, much like building an engine DIY, if you want good, lasting results. If you dont have them, or can't source them, then take it to a shop.
     
  12. 71skylark3504v

    71skylark3504v Goin' Fast In Luxury!

    First of all, I am always glad when you reply to A/C threads.

    On the Ranger, I relied solely on a system purge to rid the system of air and other contaminants. I know this is against the rules but I did it. Of course I wonder about the longevity of the compressor too, but it's a $4k truck and I am not really worried about it. Making do is a gamble sometimes, just the way it is.
     
  13. Briz

    Briz Platinum Level Contributor

    You guys do what you want. I am a state licensed A/C contractor and federally certified to handle and transition refrigerants.
     
  14. ranger

    ranger Well-Known Member

    Hi folks,

    Well, this has been an interestesting and useful thread. It is all the more relevenat as many of us want to keep our original R-12 systems.

    Let me add one more variable to the mix. Our local auto-store sells something called "Freeze 12." It has some R134 in it but is mixed with something(s) else. It comes in small cans and you have to buy an inexpensive adapter to hook it to your manifold gauges. They claim (the emploees and the manufacturer) that it can be added as a direct substitute for R-12 and that no change to PAG or Ester oil is required.

    I've spoken to several people who have used it and they have had good results.

    Now, the reason I just don't take it to an A/C shop to find the leak is that they won't do it. No shop in my area has cylinders of (recycled and cleaned) R-12 that they can inject and then evacuate. This became an issue when the A/C changovers started getting popular years ago. There were a lot of "exotic" blends of "R-12" that would contaminate pure R-12 that was in evacuation machines. I know that the Snap-on a/c machine I last used 10 years ago could test for contaminants in the R-12 so that we could choose to contain them in another cylinder for proper disposal, as we didn't want to contaminate cylinders of pure R-12 with the myriad mixes we were seeing.

    I just may use Freeze 12 to test my leak as it appears it will not contaminate the oil in my system.

    Thanks, again.

    Ranger
    Aiken, SC
     
  15. lsrx101

    lsrx101 Well-Known Member

    Ranger,
    Freeze-12 is a blend of R134a (80%) and R142b (20%). It came about in the early 90s when R12 was being phased out, as did a lot of the other strange and exotic brews. It's a really good product for what it was designed for. It would be fine for leak testing an R12 system, you can even run the system to monitor the performance before evacuating and charging with R12. I use it for exactly that purpose on R12 systems. It's no more "harmful" than virgin R134a for leak testing, but also no less "harmful".

    Here's the lowdown on Freeze-12:
    The problem with using R134a in an R12 system is that the mineral oil used with R12 will not be carried through the system by R134a. (description in a nut shell). When converting to R134a, the mineral oil must be flushed out and PAG oil must be installed to lube the compressor. It's labor intensive and costly if you're paying someone else to do it.

    Freeze-12 kinda solved that problem. The R134a does the cooling and the R142b combines with the mineral oil to carry it through the system. Win-win! You could fix a minor leak, pull the system down and charge it up with Freeze-12 and be good to go. You got the convenience of R12 with the performance of R134a. However, It can't cool any better, or worse, than R134a because that's what it is for all practical purposes.

    The problem with Freeze-12 TODAY is that automotive R12 systems are all 18 years old or more. They usually need more than a simple leak repair to make them reliable again. It would be silly to overhaul an R12 system, install mineral oil, then use Freeze-12. R134a and PAG oil would yield the exact same result for a bit less $$$, and would adhere to an industry standard. All of the other typical R134a conversion issues still apply to both refrigerants (POA valve, TXV, condenser efficiency, etc).

    ---------- Post added at 12:05 AM ---------- Previous post was at 12:01 AM ----------

    Briz,
    I hope I didn't step on your toes. If so, I sure didn't mean to. I respect your input and knowledge very much. If I did, I apologize.
    I wasn't advocating mixing any refrigerants, just using a detectable gas for leak detection. I was also taught that CA was not acceptable for leak detection. I'm a federally licensed MVAC Tech and hold my work to a high standard, just like yourself.
     
  16. ranger

    ranger Well-Known Member

    ISRX 101,

    Thank you for taking the time to compose this informative reply. I will indeed use Freeze 12 for my leak detection.

    I wonder if you might be kind enough to answer a related question? Many Buick guys may have this same question.

    I have a 1991 Honda that blew the compressor. I bought a used compressor, put in a new dryer, PAG oil and R134A, just in case I developed a leak (I didn't want to waste the R-12).

    It's been fine for 3 years now but I do notice the cooling isn't as efficient as with R-12 and I believe this is a proven fact.

    What would I have to do to be able to put R-12 back into it? When I changed to R134A I did not flush the entire system--just replaced the compressor and dryer, as I said.

    Thanks!

    Best,

    Ranger
    Aiken, SC
     
  17. lsrx101

    lsrx101 Well-Known Member

    R12 and PAG oil don't play well together. I've never actually seen it, but I'm told that it will form a nasty goo in the system. This is why Ester oil is specified for R134a conversions, to reduce the chance of reaction between PAG and residual R12.
    To revert back to R12, you would have to totally solvent flush the system and oil flush the compressor multiple times.

    As far as using Freeze12 for leak testing, be sure you have a way to reclaim it. Most shops don't have the equipment to dedicate to Freeze12 and you shouldn't just vent it. I just happen to have an old spare recovery unit that I use for Freeze12. I forgot to mention that.
     
  18. ranger

    ranger Well-Known Member

    Dear ISRX,

    My bad; I did indeed install Ester oil and not PAG oil in the aforementioned Honda conversion. Would this affect your answer or would I still have to completely flush the system?

    Unfortunately, while I agree with you that the Freeze 12 should be recoverd, I don't have the equipment to do that nor, do I believe, any shop in S.C. has.

    This is a small and poor state. Out of all the cars that head to the junkyards down here, I don't want to hazard a guess on the percentage of cars from which they recover the R134, R12, or whatever "exotic" mix may be in the system, though I would think it would comprise about 10% of the cars. I'm only guessing, of course, but I do spend a good bit of time there and I do notice what goes on.

    Hell, as I said, our shops don't have any desire or equipment to recover/clean/recycle R12--though many of these shops certainly did just a few years ago. It's a question of economics, of course.

    In any case, I thank you, again, for you knowledge and the education you have given me.

    All the Best,

    Ranger
    Aiken, SC
     
  19. lsrx101

    lsrx101 Well-Known Member

    xxxxxxxxxxxxxxxxx

    ---------- Post added at 10:13 PM ---------- Previous post was at 10:11 PM ----------

    ]Dear ISRX,

    My bad; I did indeed install Ester oil and not PAG oil in the aforementioned Honda conversion. Would this affect your answer or would I still have to completely flush the system?

    Youre good to go wit R12 or R134a, then.

    Unfortunately, while I agree with you that the Freeze 12 should be recoverd, I don't have the equipment to do that nor, do I believe, any shop in S.C. has.

    This is a small and poor state. Out of all the cars that head to the junkyards down here, I don't want to hazard a guess on the percentage of cars from which they recover the R134, R12, or whatever "exotic" mix may be in the system, though I would think it would comprise about 10% of the cars. I'm only guessing, of course, but I do spend a good bit of time there and I do notice what goes on.

    Hell, as I said, our shops don't have any desire or equipment to recover/clean/recycle R12--though many of these shops certainly did just a few years ago. It's a question of economics, of course.

    I agree. However, since i'm a "professional", I'm supposed to make you aware of the "right" way to do things.

    In any case, I thank you, again, for you knowledge and the education you have given me.
    I sure hope it helps. :)
    All the Best,
    And to you, too!

    Ranger
    Aiken, SC
     
  20. ceas350

    ceas350 "THE BURNER"

    As another ac tech I will step in and say briz is right... refridgerant doesn't blend with the oil like gin and orange juice. Lol but it mixes like carbonation and s bag of sprite in a fountain machine. This is why you should not use 134 if you plan to use 12 for the rest of the duration. I will find some video or somethin to show what I'm talkin about.
     

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