R134 on top of R12

[Maindrian Pace]

Has anyone ever mixed the two? My A/C is a little low, still cold but in the 50s at the vent, not as cold as it should be. I have a few cans of R12, but I don't want to waste a whole can if it only needs a couple of ounces, so I wonder if a small amount of 134 can be added on top of the R12; just feed it in slowly until the temp drops a few degrees. Not a lot of information on this on the interwebs, other than "don't do it or it can explode and cause a black hole that will suck up your whole neighborhood" Or something to that effect.

 

[Snotty]

From what I've been told, no! Thou shall not do so!

 

[3C's & a D?]

It's worth trying if you don't like your car.

On the serious side, they have completely different properties and cannot be mixed. I wouldn't even try it "just for fun" on a parts car in the northern climes of Alberta, let alone Arizona. Not worth it.

 

[mrfury68]

Don't do it! Different molecular structure of the freon and the oils are not compatible at all. If you have R-12 use it. Leave the can on the charging hose and close the valve if you don't use it all. Be careful not to overcharge it either.

 

[Trace 300 Hurst]

12 and 134 themselves are completely compatible in that they will mix and possibly provide you a little cooler air.

However, the oils required for either are not at all compatible and if you mix in some 134, it is now operating in a mineral oil environment instead of the required PAG oil. Don't do it or it can explode and cause a black hole that will suck up your whole neighborhood.

Go ahead and use a can of 12. I think you'll be surprised and pleased to see that when the receiver sightglass bubbles stop and you then continue and add the needed additional half-can, you'll have used that full can of 12. This rule-of-thumb for "a half can after the bubbles stop" is because you're not starting from an empty system that would required 3 lbs, 2 oz, which is essentially a half can more than "bubble stop". You have no idea the volume of gas in your system right now, so the bubble stop plus half is the standard for the past 60 years. Use your R12 and be happy.

 

[CBODY67]

Usually, when our '66 Newport was a used car, when it'd start to get a bit warm on the vent temps, it would usually take right at a POUND of R-12 to get it back right. So if you are worried about using a partial can, you'll end up needing close to the WHOLE 16oz (back when cans had that much in them!!!).

The other thing about refrigerant oils, should the incorrect gas get into the system, the oil will congeal and settle to the lowest point it can get to. As in condenser and eraporator, thereby reducing the total cooling capacity of those two items. That was one of the things a friend in the automotive refrigeration industry told me years ago.

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CBODY67

 

[Maindrian Pace]

Thanks for the advice gentlemen. I'll go ahead and use the R12, and if there is any left over, I'll put it in another car around here that is still R12 - although I have converted most of them. I've always been a little paranoid about over charging, but I've never heard the half can after bubble stop rule, so I'll give it a go.

 

[Carmine]

Should be no issues mixing these refrigerator repairman do it as well, and those are pickier than automotive AC

 

[Trace 300 Hurst]

Thanks for the advice gentlemen. I'll go ahead and use the R12, and if there is any left over, I'll put it in another car around here that is still R12 - although I have converted most of them. I've always been a little paranoid about over charging, but I've never heard the half can after bubble stop rule, so I'll give it a go.

Please let us know if you swallow that whole can, as I suspect you will. As you probably know, 50 at the vent is not cool enough for these big, lots-of-glass, air leaky, poorly insulated old cars. 50 would probably give you about 80 in the cabin on a warmish, sunny day. And a humid 80 at that. You might be using two cans!

 

[Maindrian Pace]

Thanks Trace, I will.

 

[Trace 300 Hurst]

Should be no issues mixing these refrigerator repairman do it as well, and those are pickier than automotive AC

I think you are mistaken with your take on this. I watched the vid.

1. The system in this junkyard car was empty, or very near to it. There was not enough system pressure to trigger the low-pressure cutout switch. So let's assume the system was empty due to the leaking compressor front seal. Front compressor seals don't like to sit, and certainly not for 9 years or whatever. As was said in the vid, he added 152 and, not surprisingly, it began to work. And he added can each year as a top-off, so we know it was leaking and continued to leak. He did note that it required less 152 year after year because possibly that finicky seal started to "wear in" again after sitting so long.

2. 152A requires PAG (or POE) oil, which is what was in that system because it was a 134 car. If had been wax-free mineral oil (required for R12) it wouldn't have worked for long. Certainly not 7 years.

3. Ultimately, he decided to replace the compressor due to a tapping noise, not wanting to trash the whole system if the compressor were to grenade internally.

4. Despite the flammability issue (which I don't think is a big deal, but others are apoplectic about this ), 152 will work in a 134 system because the oil is compatible with both refrigerants. It is my guess that a little 134 (if there was any in there) would work just fine with the majority 152. It's also my guess that a 50/50 mix might work, too, if it didn't start freezing up the evaporator, overheating the compressor, or causing some other nefarious *refrigeration" issue not associated with the oil.

Sidebar: The oil in an AC system doesn't sit in the compressor sump like an engine oil pan, simply lubing the moving parts and going back down to that pan. In an AC system, the oil and the refrigerant MIX TOGETHER into an emulsion and move through the lines, condenser, evaporator, and the compressor as "one fluid". So....if the oil is not compatible to absorb and mix with the refrigerant, you have a big problem as was mentioned in Post #6, above.

 

[Carmine]

The Buick in the video is a late 80s R12 car, pulled from a junkyard with an already replaced, low-quality reman compressor. I won't argue the point about replacing the oil, but as a top-off, it's hard to imagine it causing an issue. Ditto for flammability.

 

[david hill]

As far as I know there IS NO DROP IN REFRIGERENT. In my getting my certifications years ago I was told under no circumstances to mix 134A and R12. The properties of each refrigerant are quite different as 134a is more volatile than R12. Simply don't do it. AS for being flammable check the contents on the can. Any combination of combustible gases is a BIG red flag.

 

[CBODY67]

There used to be "acceptable drop-ins" to replace R-12 with. In the a/c forums back then, some were even using butane as a refrigerant, no matter the issues of flammability in a collision situation! But R-12 has a flammability issue, too, from all of the cautions of using it around an open flame, although many earlier leak detectors used a sniffer tube to a small open flame on the protected end of a gas torch.

In those earlier times, there were lots of "I know better than them . . . " orientations. That was 30+ years ago. LOTS has been figured out since then!

Now, it was openly known that one of the approved drop-ins was a MODIFIED R-134a gas, but not a normal R-134a gas. Some might have took that to mean that normal R-134a was approved, or should have been. NOT knowing about the issues with the refrigerant oils, apparently.

Personally, I'm more intrigued by the R-152a and where it came from?

CBODY67

 

[Maindrian Pace]

Someone asked what oil the Youtube presenter was using, mineral or PAG. I was wondering the same thing.

Q - Did this system still have the R12 mineral oil in it, or did you use PAG or something else?

A - This one was already charged with R134A and some conversion oil when I got the car. These systems need good oil miscibility so using R152A would need PAG or POE oil. When I finally did replace the compressor I flushed the whole system and went back with PAG oil. Not to confuse things, but with small electric refrigeration compressors can use R152A with original mineral oil, because they don't depend on oil miscibility like the car A/C does.

 

[Trace 300 Hurst]

The Buick in the video is a late 80s R12 car, pulled from a junkyard with an already replaced, low-quality reman compressor. I won't argue the point about replacing the oil, but as a top-off, it's hard to imagine it causing an issue. Ditto for flammability.

View attachment 591417

The Buick had been converted to 134 before he got involved (you can see the conversion fittings in earlier vids), meaning it had PAG in it, meaning the 152 was just fine with it. It's likely that 152 would work with mineral oil. I **think** I've seen that done, but don't recall for sure. Butane and propane does work with mineral oil, but that's not the subject here. Anyway, the conversation is about mixing 134 with an existing undercharged 12 system, and as we've all agreed, that's a non-starter due to the oil issue.

 

[Carmine]

The Buick had been converted to 134 before he got involved (you can see the conversion fittings in earlier vids), meaning it had PAG in it, meaning the 152 was just fine with it. It's likely that 152 would work with mineral oil. I **think** I've seen that done, but don't recall for sure. Butane and propane does work with mineral oil, but that's not the subject here. Anyway, the conversation is about mixing 134 with an existing undercharged 12 system, and as we've all agreed, that's a non-starter due to the oil issue.

Yes definitely agree no mixing R12 and 134.

 

[Trace 300 Hurst]

If we assume that Buick Park Avenue David knows what he's talking about, and I believe he does, this is his take on the whole subject.

 

[Gerald Morris]

There used to be "acceptable drop-ins" to replace R-12 with. In the a/c forums back then, some were even using butane as a refrigerant, no matter the issues of flammability in a collision situation! But R-12 has a flammability issue, too, from all of the cautions of using it around an open flame, although many earlier leak detectors used a sniffer tube to a small open flame on the protected end of a gas torch.

In those earlier times, there were lots of "I know better than them . . . " orientations. That was 30+ years ago. LOTS has been figured out since then! ....

CBODY67

My step dad used propane as the refrigerant in his '74 Ranchero, and numerous other older automotive AC's. I ran it in my '66 NYer, as it has a leaky AC. It ran cold, until it leaked too badly to warrant risking it any longer. I then pulled the old compressor off that 440, though I sold it with the car that Fall. That was the ONLY air conditioned vehicle I have ever owned since 1977. 'Twas novel, comfy, and just not worth the bother to me. I LOVED freaking youngsters out by telling them they were riding in a propane cooled automobile! As if riding with me isn't dangerous enough anyway....

Ammonia cools best of all, but isn't too portable.

 

[volksworld]

cbody67 the concerns with r12 and a flame weren't due to its flammability but the fact that it+mineral oil+fire= phosgene nerve gas