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Good A/C Flush Solvent

I just joined the forum. Thanks for having me!
I need to flush my R-12 A/C system. I am converting back to R-12 from a R-134A conversion. All the mineral oil, Ester and/or whatever other oil is in the system needs to be completely flushed out. I’m seeking which solvent you folks would suggest? Are the expensive store bought solvents really better than something like 100% isopropyl alcohol, lacquer thinner or mineral spirits? And if the expensive ones are better, can anyone suggest which brand?

Thanks kindly in advance!

Can you still find R12? I thought that stuff was illegal now. It must cost a fortune to get any today. Why cheap out on solvent if your going to pay out the roof for R12?

Frankly, this is one of those questions where if you have to ask you shouldn’t be doing it.

There is no good reason to change a system back to R12. R134A is the way to go. If you have a Fiero then R134A will freeze you out of the vehicle in no time at all.

This is the product I use to flush AC systems.

Alcohol, laquer thinner, or mineral spirits won’t remove or neutralize any acids that may be in the AC system. And you don’t want to use anything that may leave a residue in the AC system.

You can still get R12 refrigerant. But you have to be licensed to purchase it, and it ain’t cheap.


Tester - Thanks kindly for your reply. I had my list narrowed down to the FJC product you suggested or the Four Seasons Dura II flush. Both have good reviews, but like anything it’s always nice to get a second opinion.

Thanks again.

FieroWilliam…just tell us why you are trying to convert back to R12. I’m curious and others probably are too.

Me too. I did a 135 conversion on my late 1990 taurus lx. It worked great. Why go back?

Refrigeration systems were never designed to be “flushed”…Oil pools in the compressor and it stays there forever unless you take it apart…If you do it right, R-134a works just fine…

“Refrigeration systems were never designed to be flushed.”

A refrigeration system is flushed when a compressor fails to remove the debris from the failed compressor. So the compressor is being replaced anyway.

The alternative is to replace every component that makes up the AC system.


I have three 88 Fiero GT’s. One has R-12, but the other two have been converted to R-134. The one with R-12 has killer A/C! R-12 gets colder faster and blows colder. This is not a coincidence. One of my other Fiero’s was on R-12 when I bought it. It used to have equal performance before being converted. The two cars now on 134 slowly get cold, but not nearly as cold and as fast as the R-12 cars. And because of the pressure differences between 12 and 134, the pressure switch on the drier has to be adjusted to make the system pump for longer, but performance is still weak compared to the R-12 car.

Fiero A/C has a common leak area. One I was not aware of until recently. Before I knew of this, I was encouraged to convert because of the expense of R-12 vs. 134. With the leaks now isolated and repaired, I’m certain the systems are 100%.

Additionally, I’m not certain if the shop that “converted” one of my systems over did anything more than a quick vacuum and dumped the 134 in. I believe the original mineral oil is still the only lubricant in the system. Research has told me that mineral oil does not get moved around the system well with 134, which is why people shoot a can of Ester into their system. That car is bound to suffer compressor failure soon if not addressed. The other car appears to have an abundance of filthy lubricant in the system, but I have no idea what it is because It was converted before I bought it. Between the poor performance of R-134 and these other unknown variables, I’d rather just switch back. Not to mention the equipment and an excess of R-12 are easily available to me.

Mineral oil used in R12 systems doesn’t mix with R134a refrigerant. So this can lead to a lack of lubrication to the compressor. And if you just add ester oil to the mineral oil already in there that’s too much oil. And too much oil effects AC performance.

If you’re not sure what oil is in the system, then I would remove the compressor and drain the oil. Flush the AC system and compressor. Add the proper amount of ester oil to the compressor. Replace the orifice tube with a R134a orifice tube. Add the ounces of oil to each component as required. Pull a vacuum on the system and charge it with R134a.


There are no orifice tubes for this car available which specify they are for 134A.
The plan is to drain/flush well, replace orifice tube, drier and recharge with R-12 and mineral oil.

My 06 Subaru Baja and 97 Jeep were designed to use R-134A, and those systems do work well… But for the R-12 systems, until an oversized condenser is available, I’m sticking with R-12.

Or as it’s also known as, “Liquid Gold”!


I’m going to say this straight: Whoever’s dropping the disagrees and offtopic flags in this thread is a moron. The posts in question had good advice, and were spot on. Converting back to R12 is not only a bad idea, but it’s most likely illegal to take a compliant system and intentionally revert it to a banned system.

Cigroller was also correct that if you have to ask how to service an air conditioner, you shouldn’t be messing with it. Leave it to the professionals if you don’t know how.

This thread is a classic example of why the internet-teenager rating system is a bad idea on this forum.


R-12 systems are repaired all the time by qualified licensed technicians. My circumstances are exactly the same except for the initial system cleaning and preparation. I’ll have the R-134A recovered in a legal fashion and the replacement R-12 dispensed in a legal fashion. There is nothing “illegal” about it.
You and Cigroller completely missed the key question here, so go back and read again. I never asked HOW to service the air conditioner. I simply asked WHAT cleaning solution people would suggest. I came here for an experienced opinion, my first mistake quite possibly.

I came here for an experienced opinion, my first mistake quite possibly.

Actually FieroWilliam, I’ll say that I’ve been on lots of auto boards. For quality of expertise this board is hands down the best. Hang around here for a few days and get to know the what goes on here. If you did, you’d have presented your initial post differently. You would have explained that you have a shop to do all of the actual refrigerant servicing but that you are doing the prep work.

I you hung around you’d see all sorts of crazy people trying to do things that they shouldn’t do - dangerous things. Unwise things. Self-defeating things. And even illegal things. On the face of it, your initial post gives no one any way to distinguish you from the daily stream of wackos with poor judgment and no knowledge.

So re-read the posts knowing something a little about this “place” - and then I think you’ll have a better understanding of where people are coming from. I absolutely did not miss the key question. People here try to give responsible advice - as in not helping people do bad (by whatever definition) things. Try some home HVAC boards. You’ll see that a lot of them have a strict “no DIY advice” policy. With good reason.

My A/C shop guy runs R12, btw - for exactly the reasons you gave. (Of course, he’s about 80 and spent most of his life working with/on R12 systems).


Message received and noted. You are right, I didn’t read many discussions here before posting my question. But I also didn’t realize my abilities would be so heavily critiqued either.

I’ve had a lot of experience working on cars. If I can change the clutch on a Fiero by myself, I’d say I’ve got some know-how. That said, I’ve never flushed an A/C system. And with the vast amount of products on the market, I figured a second opinion couldn’t hurt. That is what led me here.

Thanks for the offer. I’ll stick around and ride this roller coaster for a while.

They sell R-12 in Mexico in handy 1-Kilo or 10 kilo cans…It’s used for all kinds of refrigeration systems, including liquor store beer coolers…The Ozone Hole went away and now the save the planet folks want to ban the release of carbon dioxide…They have decided R-134a is bad too so that’s about to be replaced with something that costs two or three times as much and requires new equipment to service…

The problem with automotive systems is that sooner or later, the refrigerant ends up in the atmosphere…


I’ve seen some of that Mexican R-12. Sometimes the can says R-12 on the label, but they have a screw top just like 134A cans. R-12 cans are supposed to have a flat top that utilizes a tapper which pierces the can, not screws on to it.

Yep, R-1234, the R-134 replacement is slowly creeping into the marketplace.
The times they are a changin’!