Help! Newbie-- A/C 134 back to R-12 help needed

[vettebob]

Hi,

Just bought a 1987 Corvette and the owner had converted the A/C to R-134. I want to convert it back to R-12. I have gauges, vacuum pump, and access to R-12. Can anyone outline the process to convert this car back to the original R-12??

Please, I know there is a huge controversy about R-134 versus R-12. I just want to convert back to the original R-12...

Thanks a bunch in advance!
vettebob

 

[G Winter]

If it works leave it alone. I have never heard of anyone switching back but without knowing just how they went about it you could end up with a mess. At the very least you are going to want to flush the system, and replace the dryer.

Glenn

 

[joshwilson3]

I would leave it. You will need to replace the dryer, flush the system. Replace the orifice. Put a vacuum on it and check for leaks. And I think you might have to replace the orings. I know you do when you convert from R12 to R134.

 

[GerryLP]

Yes, what gives?

Even if you have the original R-12, it probably is not worth converting back. I had the A-C shop evacuate the old R-12, and they put FR-12 back in. Apparently almost the real thing, but legal.

GerryLP:cool

 

[joshwilson3]

Yes, what gives?

Even if you have the original R-12, it probably is not worth converting back. I had the A-C shop evacuate the old R-12, and they put FR-12 back in. Apparently almost the real thing, but legal.

GerryLP:cool

Haha. FR-12 is nothing like R-12. Because FR-12 is nothing more than a blend of R-134a and HCFC 142.

This is what I found:

FR-12 = 59% R-134a, 39% HCFC-124 and 2% butane.

I'd much rather have R-134. No point in having multiple gases in your system. You even have to watch out for the R-134 cans they sell at the parts store as they usually are full of other things like sealants. To get pure R-134, you usually have to get it from a shop.

 

[gmjunkie]

If it works leave it alone. I have never heard of anyone switching back but without knowing just how they went about it you could end up with a mess. At the very least you are going to want to flush the system, and replace the dryer.

Glenn

Most Retro Fits are Half A$$ed at best!
If retro fitted Correctly,"It'll Freeze the Balls off a Brass Monkey"!!

 

[toptechx6]

Okay, I'll be the one to disagree and attempt to answer the OP, it is after all his choice, perhaps he participates in NCRS events, or perhaps the conversion does NOT cool as well as the original? No matter, the decision is his to make.
I think the minimum would be to flush the system of oil, that would also entail replacing the accumulator and removing the compressor to empty it then refilling with mineral oil. Might be a good idea to add a few extra ounces to make up for oil that flushed from the condenser, evaporator & lines.
As far as I know the 134A o-rings and seals should be compatible with R12, at that point pull a good vacuum & recharge based on original capacity.
At least that is how I would tackle the job, good luck.

 

[GerryLP]

Haha. FR-12 is nothing like R-12. Because FR-12 is nothing more than a blend of R-134a and HCFC 142.

This is what I found:

FR-12 = 59% R-134a, 39% HCFC-124 and 2% butane.

I'd much rather have R-134. No point in having multiple gases in your system. You even have to watch out for the R-134 cans they sell at the parts store as they usually are full of other things like sealants. To get pure R-134, you usually have to get it from a shop.

Interesting...I did not know that. However, given the fact that we're talking about A-C systems, I would not be surprised if the same info could be found about all other compounds used to make refrigeration work. I am no chemist (my brother Jorge has those honors), but they are all compounds of some sort, que no? Here is some information which seems to back-up what you were told.

R-12 dichlorodifluoromethane

http://www2.dupont.com/Refrigerants/en_US/assets/downloads/h45945_hfc134a_push.pdf

And here is also an interesting anser to the question,"what does 134a means?"

What does 134a stand for in refrigerant HFC-134a? - Yahoo! Answers


All I know is that the A-C works the same as it did with regular R-12 (which we all know it was not like today's cars). :ugh

GerryLP:cool

 

[gmjunkie]

Might be a good idea to add a few extra ounces to make up for oil that flushed from the condenser, evaporator & lines.

Why Not Do it Right or Just Don't Do It??Too much refrigerant oil can kill a system too!!:L:L:L

 

[toptechx6]

Why Not Do it Right or Just Don't Do It??Too much refrigerant oil can kill a system too!!:L:L:L

And that is exactly the way I would do it. My 93 service manual indicates adding 1 oz. for oil in the condenser and 3 oz. for that in the evaporator, but since I don't have an 87 manual perhaps you would be kind enough to provide the correct amounts for the OP?:eyerole

 

[Rex S]

If your system isn't cooling well the 134a hasn't been set up porperly. The math conversion for 12 to 134 is a basic and then the system needs fine tuned one ounce at a time.

If you want to do this because 12 is the "correct" refrigerant, you need to have a known supply of name brand, old R12. DO NOT use the eBay stuff being sold cheaply as R12! It is off shore refrigerant and the chemical makeup is unknown.

I really don't understand the question since there is no reason to go back but the choice is yours. If it's a restoration thing for judging, why not just take the adapters off for showing (if you can get them off with out destroying the ports) and put the stock caps back on? If the judging comes down to what the chemical make up is in the A/C system, the cars must be outstanding! Hope no one has unleaded gas or Mobil1 in the car!

 

[gmjunkie]

I think the minimum would be to flush the system of oil, that would also entail replacing the accumulator and removing the compressor to empty it then refilling with mineral oil. Might be a good idea to add a few extra ounces to make up for oil that flushed from the condenser, evaporator & lines.

Ok Then,Witch is it?? Fill the compressor and add EXTRA Refrigerant oil around the system,or use the correct amount of Refrigerant Oil distributed evenly 3-4 places around the system??
PS If you flushed the system without removing the Orifice tube or Condenser,You've just took a chance of leaving residue that looks like what BP has done to the Gulf!!:L:L:LCondenser must come out of vehicle to flush it right,the Evaporator can be left in the vehicle,but the orifice tube must be removed for All residue to be Flushed from system!!

And that is exactly the way I would do it. My 93 service manual indicates adding 1 oz. for oil in the condenser and 3 oz. for that in the evaporator, but since I don't have an 87 manual perhaps you would be kind enough to provide the correct amounts for the OP?:eyerole

Well, the Delco R4 compressor system used from 84-87 uses 6 oz Refrigerant Oil,where your Denso uses 8 or 9 oz!(According to the tag on the back of the compressor on my 92!But I'd have to remove the ASR to see the tag clearly and It ain't Broke,So I ain't fixing it!:L) I use ester refrigerant oil in everything because it is compatible with both R12 and R134a,where Mineral Oil is only compatible R12 and PAG refrigerant oil is only compatible with R134a!! Witch in his case,I would add 1 1/2 oz refrigerant oil to Compressor after throughly draining it,1 1/2 Oz to Condenser,1 1/2 oz to evaporator (with NEW R12 Orifice Tube), and finely 1 1/2 Oz to Dryer/Accumulator install and seal system up,Evac, Recharge with correct amount of refrigerant!!

 

[vettebob]

Well, thanks for all the myriad answers. I knew people were going to have to jump in with comments about R-134. I have access to Dupont R-12, and that is what I want to use.

Would the pressure switch have been changed when the system was converted, or just the "O" rings and orifice tube?? (and oil, refrigerant)

What is a good flush agent, and where is the best place to buy ester oil??

Thanks again,
vettebob

 

[gmjunkie]

Well, thanks for all the myriad answers. I knew people were going to have to jump in with comments about R-134. I have access to Dupont R-12, and that is what I want to use.

Would the pressure switch have been changed when the system was converted, or just the "O" rings and orifice tube?? (and oil, refrigerant)

What is a good flush agent, and where is the best place to buy ester oil??

Thanks again,
vettebob

You can get ester refrigerant oil at most any automotive parts store,along with a orifice tube!!
As far as the low pressure cut out switch, you may have to adjust it or maybe not,Most retro fitters don't change the settings (17-18# R-12) to (21-22# R-134a)so it could be right for R-12!!Just have to get a charge on it and see!! Turning the screw Counterclockwise will lower the cut out pressure,Clockwise will raise the cut out pressure,1/8 turn is approx 2 lb!

Flush Solvent,I use FJC Automotive AC Flush,you can buy it in qt's at some auto parts stores,I get mine in bulk from a dealers supply house!