As the availability of the deprecated refrigerant R134A declines, some of us will still be running R134A systems -and- quite a few more will be running R134A in their “upgraded” R12 systems with compatible oil.

My 1994MY XJ40 started out 12 yrs ago with no A/C due to a holed condenser. After repairing the condenser, I purchased a new receiver/dryer, some PAG oil, a vacuum pump/set of manifold gauges and some R134A. A/C worked again.
I’ve refilled the system one more time since doing the original work, but last week it was not blowing cold anymore so I thought I’d try topping it off instead of starting with an empty system.
The R134A temperature & pressure chart is a definite must if you need to top off the system and I wouldn’t attempt “topping off” without a set of manifold gauges to read the hi and lo side pressures.

In Canada, it’s getting more difficult to source R134A unless you travel to the States to buy it. Eventually however, it’ll be phased out in the USA too. I tried importing a case from eBay last week and it got sent back as restricted cargo, so I started thinking about alternate solutions.

After some research into using “duster” (R152A; diflouroethane CAC 75-37-6) as a refrigerant, it seems that not only is it fully compatible with R134A (incl. seals and lubricants) but that you need less of it and it cools more efficiently PLUS has far less environmental impact than R134A. It can also be mixed with R134A in an existing system with no problem too.

Cautiously unwilling to experiment with R152A on my prized Jag, I thought my old Ford Explorer would be a good candidate for a test, so today I gave it a shot.
The explorer A/C called for 32oz of R134A. To get the amount of R152A needed, you multiply by 0.64,- so a full charge of R152A in the explorer would be 32 x 0.64 = 20.8oz. I had about a can and a half (~16oz?) of duster around. Today was Canada Day and everywhere was closed so I couldn’t buy any more.

Anyway, I hooked up the gauges and started the car.
The system pressure was down to about 10 on the low side, so it had some R134A in there - but not enough to start the compressor.

No matter, R152A and R134A are fully compatible with each other so I just thought I’d pop some in there to see if things improved.

The ambient temp today was about 80°f so my target pressures in straight R134A would have been 40-50psi on the low side and 175-210psi on the high side. The rule of thumb when using R152A in an R134a system is to reduce the psi figures by 10% for a given temperature range, so if I was running straight R152A in 80°f ambient, ideally my readings should be 36-45psi low side and 158-189psi hi side.

Of course after adding R152A to the system I’d be running a mix of the two, so I set my target about 1/2 way between the two ranges - 38-47psi low and about 164-200psi high. I think I put in roughly 16ozs (10oz can plus about half a 12oz) before I ran out of refrigerant. As luck would have it, this amount of R152A “duster” got the readings very close to my target pressures and gave me about 35°f at the centre vent. That’s colder than the R134A by a couple of degrees, so a great result.

So, that’s the experiment. Using the cheap and widely available R152A “duster” with the conversion formulas above will give you very cold temps. The stuff can be used in R12 systems too, but of course you have to prep the system as if you were converting to R134A (PAG oil etc). Oh - you need to pick up a side can-tapper too to get into the duster cans.

I hear that R152A in an R12 system can even make ice cubes!

Larry

 

Good stuff here Larry.

Gotta love SCIENCE.

Thanks for the intro to the magic "duster". I wasn't familiar with it. I know the day is coming when the R134 will go away just as R12 did (actually they say it doesn't really go away, it lingers in the upper atmosphere, killing ozone and contributing to global warming. Oops. SCIENCE).

I have a new compressor in the car now and a full charge of R134 (3 cans) on reserve. In the desert I must have my A/C, or else It is good to know that there is a feasible solution. Very "cool" that there is a product that is even more efficient than before and not as harmful. Remember when R134 was the latest, greatest and safest product, but could not be mixed with R12 and was not as efficient either.

Love SCIENCE! Happy Canada Day.

 

Hi, I installed a new AC system using R152a in my 1974 BMW 3.0CS last year. I took it out for a drive today and the AC didn't seem to blowing as cold as it should be so I'm thinking I need to top it off. I had charts for R152a and now can't find them and haven't been able to find any on the internet; they're there somewhere, I just haven't found them. Do you have some you can post?

Thanks!

 

I've not seen an R152A chart anywhere online.

Most people converting to R152A use the R134A temperature/pressure charts and reduce the pressures by 10%.

As you could be using either a converted R12 system or possibly a retrofitted R134A system, I can't speak to the actual quantity of R152A you'd need -but in a R134A system, the replacement quantity is generally the OEM amount reduced by a factor of 0.64.

Pressures/temperature correlation figures using the conversion factors above and reading the results as shown on your manifold gauges and cooling vents will be the best (and possibly the only) way to determine whether you have a low or overfilled condition.

To re-iterate, other than calculating the quantity req'd and filling from a completely empty system, there is no way to establish existing charge except by reading the pressures for given ambient temperatures as stated on commonly available R134a charts and reducing the pressures shown by approximately 10%. When you achieve these pressures, the thermometer at the vents should show temps in the target range.

Good luck,

Larry