Attempted R-152a "Duster" A/C Conversion....some advice....

Hello, I recently decided to go forward with an experiment I had been reading about for some time involving converting my A/C system on my 91 B2600i over to R-152a Refrigerant, most commonly found in Canned Compressed Air Duster. I felt pretty confident about the safety and other implications that might arise, and after thorough contemplation and research I had my system evacuated, receiver/dryer replaced and proceeded to add 2 cans of "Ultra-Duster" R-152a to the system thru the low pressure port. Rather than using a side-can Tap which I had seen in various videos online, I opted to use the top of an r134 "EZCHILL" can which fits perfectly on the duster can. I simply hooked up my existing r-134 hose and began the charging.

After charging the system, it became apparent I had actually over charged the system, which I have learned is very sensitive to pressure changes. After safely evacuating, checking the vent temps at 2k rpm, and repeating that process, I reached what I felt was about as good point with the pressure and vent temperature as I would get.

Driving around today in Tucson, AZ, with outside temperature reaching 99 degrees, while at speed my vent temps on high got down to probably about 59 degrees, colder with slower blower speed. Although I was disappointed I didnt get the colder temps I was expecting out of the r152, I was somewhat pleased that the experiment worked at all.

BUT....being the type who is never satisfied, I wanted to know why the vent temps were not colder than when I had the r134 in the system. This was the primary reason I had attempted this to begin with.

I decided to evacuate just a tad more of the r152....and once complete, there was yet another slight drop off in vent temps....I first thought that the system must still be overcharged, but then I noticed something which has led me to write this message right now.

As I released the pressure on the low side, I noticed the gas coming out of the valve was colorless for the first 5-6 seconds, before turning the familiar green which I assume is the refrigerant. And then it dawned on me...since I was using cans of compressed air, could the system not be operating at full capacity due to an excessive amount of compressed O2 being in the lines?

One area of concern before I began charging the system with the Duster was if I was supposed to have had vented the cans first, leaving just the refrigerant in them to be charged? Perhaps this is why in the videos I watched, a side tap was used, rather than an adapter on the top. In any event, It's my understanding that refrigerant 152a is heavier than air, and thus is should displace the air in a pressurized system....so when I do relieve pressure thru the schrader valve, would any oxygen trapped in the lines escape first? If you follow my thinking here, Im trying to vent any oxygen out that might be in the lines, without losing much r152a. And since the gas escaping at first is colorless, I assumed that would be the o2, and once it turned green, that was the refrigerant.

So far, I've done 3 more of these slight ventings of what I think is just o2, and stopped when green gas started to escape. And each time, I swear my vent temps have gone down just a little.

My question to all of you is, A)Has anyone else successfully converted to R152a? and B) Using the cans of air duster involved, would it be a natural assumption that in addition to the Refrigerant, that o2 would also be put into the system while charging using those cans of compressed air? Finally, did I miss a step, was I supposed to have vented the duster cans first, or held them a certain way whilst charging the system to only allow the r152a to flow out?

If anyone with knowledge of physics or how gasses move around in a pressurized system could respond, i would appreciate it.

Evacuate your system and don't do this again!!!!
Any refrigerant mixed with air is not designed to work in a refrigeration system.
You're gonna be lucky if the stuff doesn't have an adverse reaction with the oil and turn it into pudding!

I would not have attempted this without thorough investigating and my conclusion is that this is safe. The EPA has r152a listed on its own website as a suitable replacement for R12.

"Safe" and good replacement are different items, and you don't appear to have the knowledge and experience to do this.

Those cans of compressed "air" typically don't contain air. If such cans actually did contain any real air or just nitrogen: you still screwed yourself. You need a vacuum pump and real gauge set , plus leak detection stuff and eye protection AT MINIMUM to do AC work.



Evacuate your system and don't do this again!!!!
Any refrigerant mixed with air is not designed to work in a refrigeration system.
You're gonna be lucky if the stuff doesn't have an adverse reaction with the oil and turn it into pudding!

Trying to use a non-refrigerant to try to save a few dollars is foolhardy.

You're in Tucson, so hot climate like SinCity in Las Vegas and me in Phoenix. So you really need all the refrigerant capacity that your system - designed for R-12 - can deliver. That means spend the money to get the system evacuated (that means 30 psi vacuum for 45 minutes) and the correct amount of R-12 added. R-12 is legal to be purchased and used. I know of two shops in Phoenix (because I only know two shops) that still do R-12, but in the Phoenix area there could be several hundred.

I hope you didn't add any kind of sealer or other refrigeration oil, because if you did, you've created a huge mess because you were trying to save $50 of R-12 cost. When you look at the cost differential of R-12 compared to R134a or your air duster, plus oil flush, etc., you're really not saving anything, because refrigerant is not a consumable, it's a one-time purchase in a non-leaking system.

Let me say that this duster gas is colorless, the green would be some of your refrigeration oil mixed with it. You just can't vent off "the oxygen or nitrogen".

You made a big mistake in trying to shortcut and be cheap instead of going to a shop. Don't wah-wah about shops in Tucson won't do R-12, I doubt that. Or you could've made a road trip to Phoenix to have it done.

An A/C system is not a completely sealed system. The front seal on the compressor is designed to leak a slight amount to always have oil in the seal. Look under the hood of any old car with the compressor mounted up high. Notice that line of oil on the bottom side of the hood just above the A/C? That's the small leak from the front seal. Newer compressors are not as noticeable.

To properly repair this system you need to pull the expansion valve and drier, flush the system, replace the oil, o rings and schrader valves, then evacuate and re charge.

You can expect about 50 degrees of temp change plus or minus a little depending on weather.

Yes, and new receiver-drier, check for leaks as well. God service valve caps are also a very important item for sealing of the system. I really recommend after flushing to go back to R-12 and use R-12 type oil, will provide the best engineered performance in a climate like Tucson.

Service caps cannot hold the over 100 psi the system settles to when off and certainly not the over 150psi on the high side when running. But they do keep dirt out. Dirt is the biggest culprit in service valves (schrader valves) and they will not usually leak until they are pushed in for service, then they will seep so slight you can hardly notice it. A little soapy water will show a bubble slowing growing detecting even a very small leak.


Yes R-12 is the best for that system. 134A will cool pretty well but it takes much more system to do so. larger evaporator, fan, condenser, fan and higher idling speed to equal what the original system will do.

But even the best system is not expected to do more than about 50 degrees below the outside temp. Having the system on recirculate and having tinted windows helps the most.

The AC professionals at the largest auto AC shop in Phoenix and their Internet forum say that caps are an integral part of the refrigerant sealing system. So I defer to them.

They are, not saying they are not. But anyone with half a brain can understand that a plastic cap with a rubber seal will not hold back 100 psi. The cap is there to keep stuff out not refrigerant in.

If you think it will, just remove the schrader valve from the high side, put the best cap you can find on it as tight as you want and charge it from the low side and see how long the refrigerant stays in there.

Older Fords had aluminum caps and some steel caps with rubber seals and those were much better than the plastic caps of today but they still will not hold the refrigerant in by themselves so thinking that a leaking schrader valve will be stopped by the cap is incorrect.

I too used to work at one of the largest A/C shops in Texas, another place where A/C is used almost year round. I have worked on thousands of A/C systems over the last 30 plus years. Probably as many or more than the most seasoned tech at that shop. But it does not take a degree to figure out a plastic cap can't hold that much pressure.

One more thing. The average R-12 system runs at 250 psi on the high side. Plastic cap vs 250 psi? My money is on the 250 psi.