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Recharging the Air Conditioner R134

Old 06-04-2009, 07:52 AM
  #41  
MBDiagMan
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Sigh.........!!!!!!!

I have to chime in here although I must take the time to put on my flame suit first.

As the owner of two Refrigerant Recycle machines I CRINGE every time I hear or read where self proclaimed refrigeration experts recommend junk refrigerants such as Hot Shot, Freeze 12, Duracool, etc., etc., etc., I not only CRINGE, but I start yelling at the computer screen when I hear people recommending the use of SEALANTS in an a/c system.

The use of junk refrigerants sets up some guy for contaminating his recovered refrigerants. The use of SEALANTS, risks the total destruction of refrigerant, recycle/reclaim equipment that costs thousands of dollars.

ALL junk refrigerants fall into one of two categories; BLEND or FLAMMABLE!

The different components in BLEND refrigerants leak at different rates. This means that to put the system back in proper order after leak repair, the ENTIRE charge must be removed and recharged with the blend from scratch because the blend lost its proper ratio of components during the leak process.

Worse yet, in almost all cases a blend can not be LEGALLY recovered. FEDERAL law requires that the CORRECT fittings be used for a particular refrigerant. Almost no one ever uses the correct fittings. Also almost no one has a recovery machine set up for blends or flammables. This means a shop that is interested in keeping their license and staying out of Federal prison, can not work on the system.

It also means that if one of these junk refrigerants is drawn into a reclaim tank with R12 or R134a, the entire contents of that tank is now contaminated and must be disposed of at considerable expense.

Every person that uses a junk refrigerant, a sealant or a misidentified refrigerant is setting up a shop somewhere for potential, unfair expense. Either the loss of a several thousand dollar machine due to sealant contamination or the loss of a considerable amount of recovered refrigerant. Refrigerant is often recovered in the course of system repair and is either put back in or a certain amount of credit given to the customer. This is not necessarily refrigerant that the shop steals from their customer or gets for free, although there are always shops with less than forthright business dealings.

Causing destruction of the shops equipment or contamination of their recovered refrigerant is not only against the law because the system was not correctly labeled or fitting equipped, but it causes the shop an unfair loss. The guys in these shops are just trying to make a living. You know, put food on the table and shoes on the baby like everyone else.

Need I go into the negatives of using Flammable refrigerants?

The original poster is seeking to repair his a/c in a proper and responsible way. IMHO, the BEST way is to find the leak, repair it, make sure the drier is okay and the correct amount of mineral oil is in the system and then charge with R12.

The next best approach is to do a PROPER R134a conversion. A PROPER R134a conversion will cost more than the R12 added charge and statistically will not last very long before causing damage to the system. I should correct that, a PROPER conversion has a pretty good chance of being long lived. A backyard conversion with a few fittings and a few cans of R134a will last a season or two with good luck before causing other problems.

Sorry for the rant, but I grew up in my Dads shop in the fifties learning about auto a/c and have followed it closely for the last fifty 2. I have NEVER seen a subject where there is so much misinformation spread around.

BTW, R134a is not FREE "of the nasty stuff." It still has about 10% of what Al Gore considers to be Earth Killing of the amount found in R12. In fact in the 2012 model European cars they will be changing to still a different refrigerant than R134a. Here we go again!

My $0.02,
Doc

Last edited by MBDiagMan; 06-04-2009 at 07:57 AM.
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Old 06-04-2009, 09:23 AM
  #42  
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I have a few questions

I am going to be rebuilding the entire a/c system on my 1990 vette. this means new dryer/evaporator/condensor/lines and flushing my compressor after clutch replacement or I will just buy a NOS compressor.

I am going to be going with 134a but my question is this. How much 134a oil do I add to each replaced part of the system? also would I use later model vette denso o-rings on my compressor where the lines bolt to the top of it since a later vette used 134 and mine didn't?
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Old 06-04-2009, 11:33 AM
  #43  
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Rinse the compressor with Ester oil, not flushing agent, then just try to get out as much as possible.

I'm not sure about total volume on yours. Vettes changed under the hood in many ways. My 88 takes 2.25 pounds or 36 ounces of R12 and 8 ounces of oil. Look for a sticker on the evaporator box to get the exact amount for YOUR car. On my 88, the FSM is even wrong in this regard. I expect that your 90 is the same is my 88 when it comes to these volumes.

For sake of discussion let's assume the same volumes as my 88. Distribute the oil with about 3.5 ounces in a new accumulator, about a couple of ounces in the evaporator and condensor each adding it all up to 8 ounces.

Once everything is back together and sealed up, turn the compressor by hand in an effort to distribute the oil so that there is not liquid in the compressor.

In a converted system you REALLY need to charge by weight into an empty system. The very best way to do this is with a 30 pound can and a charging scale. Ask around and see if you have a friend or friend of a friend with a charging scale. Charge it by weight to 70% of the specified R12 charge. For a 2.25 pound (36 ounce) R12 system this means 25 ounces of R134a. Put in the 70% amount and monitor the vent temp. If needed add one ounce at a time, and don't let the high side get above about 250 or 260. The high side pressure can run away fast, so watch it closely.

The best way to charge is with the scale and with the throttle blocked to 1500 to 2000 RPM and a HIGH VOLUME fan blowing through the radiator. I have a squirrel cage fan that I use and it moves LOTS of air. That way you simulate ram air and your pressures or more representative of the real world.

My 88 is a Texas car so it has an added auxiliary fan and shrouding in front of the condensor that makes the a/c MUCH more effective than a car not from the tropics. By charging my car with 26 ounces (about 72% of R12 volume) of 134 with 8 ounces of Ester oil, I was able to get 40 degree vent temp on an 82 degree day.

The people up North where the aux fans and shrouding are not on their cars don't believe that my Vette a/c is performing so good.

You are doing all the right things, follow through and do the rest of it correctly and whatever you do, DON'T overcharge it with 134. If you have a car with the aux fan and extra shrouding, you have the potential of getting good results even from a conversion AS LONG AS the conversion is done properly.

If you use a black top seal for your Nippon and use the Nylog o-ring sealant on it, I don't think you'll have any trouble. I have never seen a green seal for this one. The Nylog sealant is icky sticky stuff, but it does a better job of sealing o-rings and seals than refrigerant oil and is not as toxic.

Keep us posted and let us know if you have more questions.

Doc
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Old 06-04-2009, 02:37 PM
  #44  
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Old 06-04-2009, 02:57 PM
  #45  
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Jeff,

Mike has offered some very good information here. I have some confidence in the information in that table because it leaves the 88 model OUT. Even the FSM gives the wrong amount for an 88. It would be nice if you could find the sticker on your car so that you can know for SURE that 36 ounces is the correct R12 amount.

My numbers in the earlier post were based on 36 oz. R12 and 8 oz. of oil, so the numbers in that post should be valid. Since you are converting to 134, start with 24 or 25 ounces of 134. If you can't find a charge scale no way, no how. Give it two FULL 12 oz. cans of 134 and test, then add VERY small amounts from the third can and test thoroughly watching the high side pressure CLOSELY. Don't let it go too high.

If memory serves me correctly, the radiator/condensor on your car are leaned back. This is not optimum for air flow, so you may not get results as good as I did. Also if your car is from cooler climates, it may not have the aux fan which helps a BUNCH.

Good luck with it and you might offer Mike some thanks for his research.

Doc
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Old 06-04-2009, 02:58 PM
  #46  
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Chart is wrong for the '89 - Service Manual was corrected by Service Bulletin and the correct charge is shown on the Blower/Evap Housing - it's 2.25lbs.
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Old 06-04-2009, 04:13 PM
  #47  
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Sun,

Yes you corrected me on my 88 and it really paid off. The FSM was wrong and the charts that I found via the internet were wrong. I never found the tag you described, but as it turned out, I charged with 26 ounces and it came out great.

Had you not pointed out the error I would have DEFINITELY overcharged it and probably still be messing with it trying to get it right.

Thanks,
Doc
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Old 06-04-2009, 05:43 PM
  #48  
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Originally Posted by MBDiagMan View Post
Jeff,

Mike has offered some very good information here. I have some confidence in the information in that table because it leaves the 88 model OUT. Even the FSM gives the wrong amount for an 88. It would be nice if you could find the sticker on your car so that you can know for SURE that 36 ounces is the correct R12 amount.

My numbers in the earlier post were based on 36 oz. R12 and 8 oz. of oil, so the numbers in that post should be valid. Since you are converting to 134, start with 24 or 25 ounces of 134. If you can't find a charge scale no way, no how. Give it two FULL 12 oz. cans of 134 and test, then add VERY small amounts from the third can and test thoroughly watching the high side pressure CLOSELY. Don't let it go too high.

If memory serves me correctly, the radiator/condensor on your car are leaned back. This is not optimum for air flow, so you may not get results as good as I did. Also if your car is from cooler climates, it may not have the aux fan which helps a BUNCH.

Good luck with it and you might offer Mike some thanks for his research.

Doc
Mine has twin fans which pull a lot of air when they are both running. I had also pondered with mounting a pusher fan on the condensor though.
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Old 06-04-2009, 05:51 PM
  #49  
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The auxiliary fan that I am speaking about is a pusher fan that is in addition to the puller behind the radiator. The aux fan also has some very effective shrouding around it.

From what I have gathered corresponding with auto a/c guys on an auto a/c website, this is the configuration for the cars sold in the hot climates such as we have here in Texas. The cars in the Northern states do not have the aux fan that I speak of.

If you DON'T have one and you rely on air conditioning, you would find it VERY effective in improving the a/c performance.

Doc
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Old 06-04-2009, 06:15 PM
  #50  
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The Aux, Pusher is useless and has nothing to do with a/c - it started as a dealer installed option following overheating complaints from autocrossers and high altitude users ('86 Bulletin). Never intended for idle or a/c and your a/c will be pumping a bunch of hot air if it reaches the threshold for Aux operation so you might as well turn the a/c off if you see these temps. A/c grounds the Main Fan when the high hits about 230 psi, and it's all these cars need. And because the fan comes on sooner and stays on longer (ground is removed at 190 psi), Coolant Temps will be 8 to 10 degrees lower than non-a/c. If it doesn't work that way on your Vette, it's broken. Also, for those who are considering a swap to R134, that gas can make some extraordinary pressures when it 95 plus. The OEM's control that by cranking on the fans at much lower pressures - generally right around 200 psi. Unfortunately, you can't do anything about that with anything before '90. There is only the one switch available and it isn't going to signal the ECM to ground the Main Relay until it hits 230 psi.
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Old 06-04-2009, 06:15 PM
  #51  
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Originally Posted by MBDiagMan View Post
The auxiliary fan that I am speaking about is a pusher fan that is in addition to the puller behind the radiator. The aux fan also has some very effective shrouding around it.

From what I have gathered corresponding with auto a/c guys on an auto a/c website, this is the configuration for the cars sold in the hot climates such as we have here in Texas. The cars in the Northern states do not have the aux fan that I speak of.

If you DON'T have one and you rely on air conditioning, you would find it VERY effective in improving the a/c performance.

Doc
I've driven my friends 1990 and in 105 degree heat got nice and cold in his car. It also never got hot while driving it either. However he still has r12 in his.
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Old 06-04-2009, 06:57 PM
  #52  
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Well maybe I've just been lucky. If it were today, I would never even consider it, but I started converting cars in the late nineties and had bought into the 134 conversion idea until just a few years ago. I had already converted this car years ago, so I stayed with 134.

In my correspondence with some guys in Boston we came to the conclusion that the reason for my success was my aux fan and shrouding. We couldn't come up with any other explanation. As I said, I can see 40 degree vent temps on a day with ambient in the low eighties.

I also pointed out that I have quite a small (72% of R12) charge in mine allowing for relatively low, high side pressure.

If the aux fan doesn't explain the success with my 88, then I have no explanation, but I also certainly have no complaints.

For those still with R12, I highly recommend staying with it.

Also, it amazes me as to how different the C4's are arranged under the hood from year to year.

Doc
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Old 06-04-2009, 08:07 PM
  #53  
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You must have your Aux Fan spliced into the Main Relay so that it doesn't rely on the temp switch; otherwise it isn't going to come on until it's past the temp it needs to make cold air. R12, with a saturation pressure of 230 psi, is something around 148 degrees. With subcooling it's probably flowing out at around 120 (maybe less, I've never bothered to measure it), so if it's waiting for the Stock temp switch to close with a Coolant Temp of 228 degrees, it's pretty much over. Not that I'm saying you can't make it work this way, but the only thing I experienced when I tried it eons ago (and with a low temperature fan switch to boot!) was an overtaxed alternator and when the voltage dropped, both fans slowed down and everything went to hell (and this was with R12). And under borderline conditions (50 or below at the Condensor) it may short cycle which on these non PCM controlled compressors isn't that fluid. To me, and for the 60 or 70 Bucks you might spend for 36 ozs of R12, I'd forego hacking up the harnesses and leave it working the way it was designed to work (or '90 to '93 can reprogram the pressure sensor signal). Regardless of what you do, this is one item where you can make it better than the Factory because all that happened there was a 10 minute suck and dump (they don't stop the line to see if it will hold a vacuum overnight or really even bother to check pressures) so spending a little time doing it right can make it better than new (and that's probably still true for most of what's rolling off of any line today)!
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Old 06-04-2009, 10:37 PM
  #54  
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There is some very good advise in this thread ~ along with some very bad!!

First if the OP can get some R12 even at $30.00 a can that is most definitely the way to go.

Your OEM A/C system was designed to use R12 not R134!

R12 is a better refrigerant than R134 even if it's bad when vented into the atmosphere. R12 is made to work with mineral oil to lube the A/C system, R134 uses a PAG type oil and these two oils are not compatible!

There is really no way to properly flush out all the mineral oil in your OEM system to then charge with R134 and PAG oil! The only way to guarantee no future problems would be to replace every component before charging with R134 and PAG Oil, not practical or necessary.

Use the R12 it's what your vette was designed for and will work the best for cooling.

You must, I repeat must, pull a vacume of 29.5mm of mercury to evacuate all the old refridgerant and moisture in the system! At the minimum you should replace the orifice tube before you do this. Now would also be a good time to replace the filter/dryer before you vacume the system. Hold this vacume for several hours, (overnight would be better) before you recharge with R12 to insure you have no leaks and or moisture in the system.

Last edited by mako41; 06-05-2009 at 06:39 AM.
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Old 06-04-2009, 11:45 PM
  #55  
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ester oil is compatible with both R12 and R134

I have R12 in the Vette and the 69 GTX
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Old 06-05-2009, 06:57 AM
  #56  
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Original R12 systems should be kept R12 if at all possible. I hope that no one got any hint from me that I was promoting conversion to R134a.

As I said before, I converted some systems years back, but my experience since that time has made me approach conversion with extreme hesitancy. Once a system has been converted, however, it is a big job to reverse convert, although I've done it on several occasions.

And Ester oil is indeed compatible with Mineral oil in a converted system. This is not ideal, but the mineral oil will not circulate, thus it will find its way into low spots and collect there. This is not ideal IMHO, but it works out okay.

I've heard tell of some synthetic oils that will work well with both 134 and 12. An acquaintance redid an a/c system using this oil and charged it initially with 134. He ran it on that during the spring 'til it got into the hotter season, reclaimed the 134 and charged with R12. He ran the system several years after that with no other work before trading the car. So, the oils are out there now.

My rule of thumb has been to use PAG in original 134 systems and Ester in conversions, but the thinking on that seems to be changing.

Although I have been lucky with my 88 and 134, I would encourage anyone with a virgin R12 system to stay with the R12.

Doc
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Old 06-05-2009, 08:00 PM
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404a kicks ***...lol
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Old 06-05-2009, 09:41 PM
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I am 58 yrs. old a vette owener and instaled 100"s of AC sys. and changed over a ton of R 12 sys, First you must vac. sys. 30 min. is cool 2ED Use change over oil and O ring cond. and leak det. all in one can at most parts stores then finsh with req. amount of freon. If all elce is ok it will work just fine. I did this to my dark bronz. c4 and it cools just great in any amount of heat. R12 is dead do not blame me it wea the gov.!! R22 or hot shot or whatever is not worth your time!!!!! PS god bless USA
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Old 06-05-2009, 09:58 PM
  #59  
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Can anyone recommend a place to have my A/C fixed ('93 convt.) - relatively close to Orange County, CA??

I am sorry to change topic here; I tried to follow the entire thread but had to realize I do not posses your DIY skills :-(.

My problems with my A/C is a long story - had it in a shop 10+ times, last 5 times at CorvetteMike's in Tustin. Had the upgrade kit installed, works for days, maybe a week - then stops blowing cold (not good in CA); currently I assume it's over-pressure with the electronics shutting it off.

Any suggestions on where to find expertise help will be most welcome.

thanks in advance - the novice...
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Old 06-05-2009, 10:02 PM
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R12 is not "dead." It is readily available with a 609 cert. which is very easy to get. $30 a pound is a bargain when you consider all the other expenses either immediately or within a few years of most conversions.

Doc
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